Catalysts and methods for polymer synthesis

ABSTRACT

The present invention provides bimetallic complexes having increased activity in the copolymerization of carbon dioxide and epoxides. Also provided are methods of using such metal complexes in the synthesis of polymers. According to one aspect, the present invention provides metal complexes comprising an activating species with co-catalytic activity tethered to a multidentate ligand that is coordinated to one or more active metal centers of the complex.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. provisional patent application Ser. No. 61/382,860, filed Sep. 14, 2010, the entire contents of which are hereby incorporated herein by reference.

BACKGROUND

Catalysts capable of effecting the copolymerization of epoxides and carbon dioxide to form aliphatic polycarbonates (APCs) have been known in the art since the 1960s. The early catalysts were based on heterogeneous zinc compounds and suffered from low reactivity, a lack of selectivity for polymer formation vs. cyclic carbonate formation, and a tendency to produce polycarbonates contaminated with ether linkages.

Improved catalysts based on transition metals have been discovered over the past decade or so. These newer catalysts have increased reactivity and improved selectivity.

Nevertheless, even using highly active catalysts such as those disclosed in U.S. Pat. No. 7,304,172, the reaction times required to make high molecular weight polymer are typically quite long. In addition, the best-performing catalysts disclosed in the '172 patent require the addition of a separate co-catalyst to achieve optimum activity.

Attempts to address these shortcomings have been made. Catalysts described by Nozaki and co-workers (Angew. Chem. Int. Ed. 2006, 45, 7274-7277) tether an amine co-catalyst to a ligand of the catalyst. These next-generation catalytic systems suffer from lengthy and complicated syntheses and undesirable induction times prior to onset of polymerization. There remains a need for catalysts that have increased activity that will further reduce the polymerization time required to produce high molecular weight APCs.

SUMMARY

The present invention provides, among other things, metal complexes having more than one metal center and comprising a tethered activating moiety. The present invention also provides methods of using such multi-metal complexes. In some embodiments, provided multi-metal complexes have activity in the copolymerization of carbon dioxide and epoxides. In some embodiments, the present invention provides a multi-metal complex having an activating species with co-catalytic activity tethered to a ligand complex that is coordinated to at least one metal center of a multi-metal complex.

In certain embodiments, the present invention provides metal complexes and methods for using the same in the copolymerization of carbon dioxide and epoxides. In some embodiments, provided metal complexes have a structure:

wherein:

M¹ is a first metal atom;

M² is a second metal atom;

comprises a multidentate ligand system capable of coordinating both metal atoms;

-   -   represents one or more activating moieties attached to the         multidentate ligand system, where         is a linker moiety covalently coupled to the ligand system, each         Z is an activating functional group; and m is an integer from 1         to 4 representing the number of Z groups present on an         individual linker moiety.

In some embodiments, the present disclosure encompasses methods for the copolymerization of epoxides and carbon dioxide, such methods comprising contacting one or more epoxides with a metal complex described above in the presence of carbon dioxide.

In some embodiments, the present disclosure encompasses methods for the formation of cyclic carbonates from epoxides and carbon dioxide, such methods comprising contacting one or more epoxides with a metal complex described above in the presence of carbon dioxide.

In some embodiments, the present disclosure encompasses methods for the formation of polyethers, such methods comprising contacting one or more epoxides with a multi-metal complex described above.

DEFINITIONS

Definitions of specific functional groups and chemical terms are described in more detail below. For purposes of this invention, the chemical elements are identified in accordance with the Periodic Table of the Elements, CAS version, Handbook of Chemistry and Physics, 75^(th) Ed., inside cover, and specific functional groups are generally defined as described therein. Additionally, general principles of organic chemistry, as well as specific functional moieties and reactivity, are described in Organic Chemistry, Thomas Sorrell, University Science Books, Sausalito, 1999; Smith and March March's Advanced Organic Chemistry, 5^(th) Edition, John Wiley & Sons, Inc., New York, 2001; Larock, Comprehensive Organic Transformations, VCH Publishers, Inc., New York, 1989; Carruthers, Some Modern Methods of Organic Synthesis, 3^(rd) Edition, Cambridge University Press, Cambridge, 1987; the entire contents of each of which are incorporated herein by reference.

Certain compounds of the present invention can comprise one or more asymmetric centers, and thus can exist in various stereoisomeric forms, e.g., enantiomers and/or diastereomers. Thus, inventive compounds and compositions thereof may be in the form of an individual enantiomer, diastereomer or geometric isomer, or may be in the form of a mixture of stereoisomers. In certain embodiments, the compounds of the invention are enantiopure compounds. In certain embodiments, mixtures of enantiomers or diastereomers are provided.

Furthermore, certain compounds, as described herein may have one or more double bonds that can exist as either a Z or E isomer, unless otherwise indicated. The invention additionally encompasses the compounds as individual isomers substantially free of other isomers and alternatively, as mixtures of various isomers, e.g., racemic mixtures of enantiomers. In addition to the above-mentioned compounds per se, this invention also encompasses compositions comprising one or more compounds.

As used herein, the term “isomers” includes any and all geometric isomers and stereoisomers. For example, “isomers” include cis- and trans-isomers, E- and Z-isomers, R- and S-enantiomers, diastereomers, (D)-isomers, (L)-isomers, racemic mixtures thereof, and other mixtures thereof, as falling within the scope of the invention. For instance, a compound may, in some embodiments, be provided substantially free of one or more corresponding stereoisomers, and may also be referred to as “stereochemically enriched.”

Where a particular enantiomer is preferred, it may, in some embodiments be provided substantially free of the opposite enantiomer, and may also be referred to as “optically enriched.” “Optically enriched,” as used herein, means that the compound is made up of a significantly greater proportion of one enantiomer. In certain embodiments the compound is made up of at least about 90% by weight of an enantiomer. In some embodiments the compound is made up of at least about 95%, 97%, 98%, 99%, 99.5%, 99.7%, 99.8%, or 99.9% by weight of an enantiomer. In some embodiments the enantiomeric excess of provided compounds is at least about 90%, 95%, 97%, 98%, 99%, 99.5%, 99.7%, 99.8%, or 99.9%. In some embodiments, enantiomers may be isolated from racemic mixtures by any method known to those skilled in the art, including chiral high pressure liquid chromatography (HPLC) and the formation and crystallization of chiral salts or prepared by asymmetric syntheses. See, for example, Jacques, et al., Enantiomers, Racemates and Resolutions (Wiley Interscience, New York, 1981); Wilen, S. H., et al., Tetrahedron 33:2725 (1977); Eliel, E. L. Stereochemistry of Carbon Compounds (McGraw-Hill, NY, 1962); Wilen, S. H. Tables of Resolving Agents and Optical Resolutions p. 268 (E. L. Eliel, Ed., Univ. of Notre Dame Press, Notre Dame, Ind. 1972).

The terms “halo” and “halogen” as used herein refer to an atom selected from fluorine (fluoro, —F), chlorine (chloro, —Cl), bromine (bromo, —Br), and iodine (iodo, —I).

The term “aliphatic” or “aliphatic group”, as used herein, denotes a hydrocarbon moiety that may be straight-chain (i.e., unbranched), branched, or cyclic (including fused, bridging, and spiro-fused polycyclic) and may be completely saturated or may contain one or more units of unsaturation, but which is not aromatic. Unless otherwise specified, aliphatic groups contain 1-30 carbon atoms. In certain embodiments, aliphatic groups contain 1-12 carbon atoms. In certain embodiments, aliphatic groups contain 1-8 carbon atoms. In certain embodiments, aliphatic groups contain 1-6 carbon atoms. In some embodiments, aliphatic groups contain 1-5 carbon atoms, in some embodiments, aliphatic groups contain 1-4 carbon atoms, in yet other embodiments aliphatic groups contain 1-3 carbon atoms, and in yet other embodiments aliphatic groups contain 1-2 carbon atoms. Suitable aliphatic groups include, but are not limited to, linear or branched, alkyl, alkenyl, and alkynyl groups, and hybrids thereof such as (cycloalkyl)alkyl, (cycloalkenyl)alkyl or (cycloalkyl)alkenyl. In certain embodiments, the term aliphatic group encompasses aliphatic groups wherein one or more hydrogen atoms are replaced with a halogen atom. In certain embodiments, the term aliphatic group encompasses chlorinated or fluorinated aliphatic groups including perfluorinated compounds.

The term “epoxide”, as used herein, refers to a substituted or unsubstituted oxirane. Such substituted oxiranes include monosubstituted oxiranes, disubstituted oxiranes, trisubstituted oxiranes, and tetrasubstituted oxiranes. Such epoxides may be further optionally substituted as defined herein. In certain embodiments, epoxides comprise a single oxirane moiety. In certain embodiments, epoxides comprise two or more oxirane moieties.

The term “polymer”, as used herein, refers to a molecule of high relative molecular mass, the structure of which comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass. In certain embodiments, a polymer is comprised of only one monomer species (e.g., polyethylene oxide). In certain embodiments, a polymer of the present invention is a copolymer, terpolymer, heteropolymer, block copolymer, or tapered heteropolymer of one or more epoxides.

The term “unsaturated”, as used herein, means that a moiety has one or more double or triple bonds.

The terms “cycloaliphatic”, “carbocycle”, or “carbocyclic”, used alone or as part of a larger moiety, refer to a saturated or partially unsaturated cyclic aliphatic monocyclic, bicyclic, or polycyclic ring systems, as described herein, having from 3 to 12 members, wherein the aliphatic ring system is optionally substituted as defined above and described herein. Cycloaliphatic groups include, without limitation, cyclopropyl, cyclobutyl, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cycloheptyl, cycloheptenyl, cyclooctyl, cyclooctenyl, and cyclooctadienyl. In some embodiments, the cycloalkyl has 3-6 carbons. The terms “cycloaliphatic”, “carbocycle” or “carbocyclic” also include aliphatic rings that are fused to one or more aromatic or nonaromatic rings, such as decahydronaphthyl or tetrahydronaphthyl, where the radical or point of attachment is on the aliphatic ring. In some embodiments, a carbocyclic groups is bicyclic. In some embodiments, a carbocyclic group is tricyclic. In some embodiments, a carbocyclic group is polycyclic. In certain embodiments, the term “3- to 8-membered carbocycle” refers to a 3- to 8-membered saturated or partially unsaturated monocyclic carbocyclic ring

The term “alkyl,” as used herein, refers to saturated, straight- or branched-chain hydrocarbon radicals derived by removal of a single hydrogen atom from an aliphatic moiety. Unless otherwise specified, alkyl groups contain 1-12 carbon atoms. In certain embodiments, alkyl groups contain 1-8 carbon atoms. In certain embodiments, alkyl groups contain 1-6 carbon atoms. In some embodiments, alkyl groups contain 1-5 carbon atoms, in some embodiments, alkyl groups contain 1-4 carbon atoms, in yet other embodiments alkyl groups contain 1-3 carbon atoms, and in yet other embodiments alkyl groups contain 1-2 carbon atoms. Examples of alkyl radicals include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, iso-butyl, sec-butyl, sec-pentyl, iso-pentyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, sec-hexyl, n-heptyl, n-octyl, n-decyl, n-undecyl, dodecyl, and the like.

The term “alkenyl,” as used herein, denotes a monovalent group derived by the removal of a single hydrogen atom from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon double bond. Unless otherwise specified, alkenyl groups contain 2-12 carbon atoms. In certain embodiments, alkenyl groups contain 2-8 carbon atoms. In certain embodiments, alkenyl groups contain 2-6 carbon atoms. In some embodiments, alkenyl groups contain 2-5 carbon atoms, in some embodiments, alkenyl groups contain 2-4 carbon atoms, in yet other embodiments alkenyl groups contain 2-3 carbon atoms, and in yet other embodiments alkenyl groups contain 2 carbon atoms. Alkenyl groups include, for example, ethenyl, propenyl, allyl, 1,3-butadienyl, butenyl, 1-methyl-2-buten-1-yl, allyl, 1,3-butadienyl, allenyl, and the like.

The term “alkynyl,” as used herein, refers to a monovalent group derived by the removal of a single hydrogen atom from a straight- or branched-chain aliphatic moiety having at least one carbon-carbon triple bond. Unless otherwise specified, alkynyl groups contain 2-12 carbon atoms. In certain embodiments, alkynyl groups contain 2-8 carbon atoms. In certain embodiments, alkynyl groups contain 2-6 carbon atoms. In some embodiments, alkynyl groups contain 2-5 carbon atoms, in some embodiments, alkynyl groups contain 2-4 carbon atoms, in yet other embodiments alkynyl groups contain 2-3 carbon atoms, and in yet other embodiments alkynyl groups contain 2 carbon atoms. Representative alkynyl groups include, but are not limited to, ethynyl, 2-propynyl (propargyl), 1-propynyl, and the like.

The term “carbocycle” and “carbocyclic ring” as used herein, refer to monocyclic and polycyclic moieties wherein the rings contain only carbon atoms. Unless otherwise specified, carbocycles may be saturated, partially unsaturated or aromatic, and contain 3 to 20 carbon atoms. Representative carbocyles include cyclopropane, cyclobutane, cyclopentane, cyclohexane, bicyclo[2,2,1]heptane, norbornene, phenyl, cyclohexene, naphthalene, and spiro[4.5]decane, to name but a few.

The term “aryl” used alone or as part of a larger moiety as in “aralkyl”, “aralkoxy”, or “aryloxyalkyl”, refers to monocyclic and polycyclic ring systems having a total of six to 20 ring members, wherein at least one ring in the system is aromatic and wherein each ring in the system contains three to twelve ring members. The term “aryl” may be used interchangeably with the term “aryl ring”. In certain embodiments of the present invention, “aryl” refers to an aromatic ring system which includes, but is not limited to, phenyl, biphenyl, naphthyl, anthracyl and the like, which may bear one or more substituents. Also included within the scope of the term “aryl”, as it is used herein, is a group in which an aromatic ring is fused to one or more additional rings, such as benzofuranyl, indanyl, phthalimidyl, naphthimidyl, phenantriidinyl, or tetrahydronaphthyl, and the like. In certain embodiments, the term “8- to 14-membered aryl” refers to an 8- to 14-membered polycyclic aryl ring.

The term “heteroaliphatic,” as used herein, refers to aliphatic groups wherein one or more carbon atoms are independently replaced by one or more atoms selected from the group consisting of oxygen, sulfur, nitrogen, phosphorus, or boron. In certain embodiments, one to six carbon atoms are independently replaced by one or more of oxygen, sulfur, nitrogen, or phosphorus. Heteroaliphatic groups may be substituted or unsubstituted, branched or unbranched, cyclic or acyclic, and include saturated, unsaturated or partially unsaturated groups.

The terms “heteroaryl” and “heteroar-”, used alone or as part of a larger moiety, e.g., “heteroaralkyl”, or “heteroaralkoxy”, refer to groups having 5 to 14 ring atoms, preferably 5, 6, or 9 ring atoms; having 6, 10, or 14 π electrons shared in a cyclic array; and having, in addition to carbon atoms, from one to five heteroatoms. The term “heteroatom” refers to nitrogen, oxygen, or sulfur, and includes any oxidized form of nitrogen or sulfur, and any quaternized form of a basic nitrogen. Heteroaryl groups include, without limitation, thienyl, furanyl, pyrrolyl, imidazolyl, pyrazolyl, triazolyl, tetrazolyl, oxazolyl, isoxazolyl, oxadiazolyl, thiazolyl, isothiazolyl, thiadiazolyl, pyridyl, pyridazinyl, pyrimidinyl, pyrazinyl, indolizinyl, purinyl, naphthyridinyl, benzofuranyl and pteridinyl. The terms “heteroaryl” and “heteroar-”, as used herein, also include groups in which a heteroaromatic ring is fused to one or more aryl, cycloaliphatic, or heterocyclyl rings, where the radical or point of attachment is on the heteroaromatic ring. Nonlimiting examples include indolyl, isoindolyl, benzothienyl, benzofuranyl, dibenzofuranyl, indazolyl, benzimidazolyl, benzthiazolyl, quinolyl, isoquinolyl, cinnolinyl, phthalazinyl, quinazolinyl, quinoxalinyl, 4H-quinolizinyl, carbazolyl, acridinyl, phenazinyl, phenothiazinyl, phenoxazinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and pyrido[2,3-b]-1,4-oxazin-3(4H)-one. A heteroaryl group may be mono- or polycyclic. The term “heteroaryl” may be used interchangeably with the terms “heteroaryl ring”, “heteroaryl group”, or “heteroaromatic”, any of which terms include rings that are optionally substituted. The term “heteroaralkyl” refers to an alkyl group substituted by a heteroaryl, wherein the alkyl and heteroaryl portions independently are optionally substituted. In certain embodiments, the term “5- to 14-membered heteroaryl” refers to a 5- to 6-membered monocyclic heteroaryl ring having 1 to 3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or an 8- to 14-membered bicyclic heteroaryl ring having 1 to 4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

As used herein, the terms “heterocycle”, “heterocyclyl”, “heterocyclic radical”, and “heterocyclic ring” are used interchangeably and refer to a stable 5- to 7-membered monocyclic or 7-14-membered bicyclic heterocyclic moiety that is saturated, partially unsaturated, or aromatic and having, in addition to carbon atoms, one or more, preferably one to four, heteroatoms, as defined above. When used in reference to a ring atom of a heterocycle, the term “nitrogen” includes a substituted nitrogen. As an example, in a saturated or partially unsaturated ring having 0-3 heteroatoms selected from oxygen, sulfur or nitrogen, the nitrogen may be N (as in 3,4-dihydro-2H-pyrrolyl), NH (as in pyrrolidinyl), or ⁺NR (as in N-substituted pyrrolidinyl). In some embodiments, the term “3- to 7-membered heterocyclic” refers to a 3- to 7-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1 to 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur. In some embodiments, the term “3- to 8-membered heterocyclic” refers to a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1 to 2 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

A heterocyclic ring can be attached to its pendant group at any heteroatom or carbon atom that results in a stable structure and any of the ring atoms can be optionally substituted. Examples of such saturated or partially unsaturated heterocyclic radicals include, without limitation, tetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl, pyrrolidonyl, piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl. The terms “heterocycle”, “heterocyclyl”, “heterocyclyl ring”, “heterocyclic group”, “heterocyclic moiety”, and “heterocyclic radical”, are used interchangeably herein, and also include groups in which a heterocyclyl ring is fused to one or more aryl, heteroaryl, or cycloaliphatic rings, such as indolinyl, 3H-indolyl, chromanyl, phenanthridinyl, or tetrahydroquinolinyl, where the radical or point of attachment is on the heterocyclyl ring. A heterocyclyl group may be mono- or bicyclic. The term “heterocyclylalkyl” refers to an alkyl group substituted by a heterocyclyl, wherein the alkyl and heterocyclyl portions independently are optionally substituted.

The term “acyl” as used herein refers to a group having a formula —C(O)R where R is hydrogen or an optionally substituted aliphatic, aryl, or heterocyclic group.

As used herein, the term “partially unsaturated” refers to a ring moiety that includes at least one double or triple bond. The term “partially unsaturated” is intended to encompass rings having multiple sites of unsaturation, but is not intended to include aryl or heteroaryl moieties, as herein defined.

One of ordinary skill in the art will appreciate that the synthetic methods, as described herein, utilize a variety of protecting groups. By the term “protecting group,” as used herein, it is meant that a particular functional moiety, e.g., O, S, or N, is masked or blocked, permitting, if desired, a reaction to be carried out selectively at another reactive site in a multifunctional compound. In preferred embodiments, a protecting group reacts selectively in good yield to give a protected substrate that is stable to the projected reactions; the protecting group is preferably selectively removable by readily available, preferably non-toxic reagents that do not attack the other functional groups; the protecting group forms a separable derivative (more preferably without the generation of new stereogenic centers); and the protecting group will preferably have a minimum of additional functionality to avoid further sites of reaction. As detailed herein, oxygen, sulfur, nitrogen, and carbon protecting groups may be utilized. By way of non-limiting example, hydroxyl protecting groups include methyl, methoxylmethyl (MOM), methylthiomethyl (MTM), t-butylthiomethyl, (phenyldimethylsilyl)methoxymethyl (SMOM), benzyloxymethyl (BOM), p-methoxybenzyloxymethyl (PMBM), (4-methoxyphenoxy)methyl (p-AOM), guaiacolmethyl (GUM), t-butoxymethyl, 4-pentenyloxymethyl (POM), siloxymethyl, 2-methoxyethoxymethyl (MEM), 2,2,2-trichloroethoxymethyl, bis(2-chloroethoxy)methyl, 2-(trimethylsilyl)ethoxymethyl (SEMOR), tetrahydropyranyl (THP), 3-bromotetrahydropyranyl, tetrahydrothiopyranyl, 1-methoxycyclohexyl, 4-methoxytetrahydropyranyl (MTHP), 4-methoxytetrahydrothiopyranyl, 4-methoxytetrahydrothiopyranyl S,S-dioxide, 1-[(2-chloro-4-methyl)phenyl]-4-methoxypiperidin-4-yl (CTMP), 1,4-dioxan-2-yl, tetrahydrofuranyl, tetrahydrothiofuranyl, 2,3,3a,4,5,6,7,7a-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-yl, 1-ethoxyethyl, 1-(2-chloroethoxy)ethyl, 1-methyl-1-methoxyethyl, 1-methyl-1-benzyloxyethyl, 1-methyl-1-benzyloxy-2-fluoroethyl, 2,2,2-trichloroethyl, 2-trimethylsilylethyl, 2-(phenylselenyl)ethyl, t-butyl, allyl, p-chlorophenyl, p-methoxyphenyl, 2,4-dinitrophenyl, benzyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, o-nitrobenzyl, p-nitrobenzyl, p-halobenzyl, 2,6-dichlorobenzyl, p-cyanobenzyl, p-phenylbenzyl, 2-picolyl, 4-picolyl, 3-methyl-2-picolyl N-oxido, diphenylmethyl, p,p′-dinitrobenzhydryl, 5-dibenzosuberyl, triphenylmethyl, α-naphthyldiphenylmethyl, p-methoxyphenyldiphenylmethyl, di(p-methoxyphenyl)phenylmethyl, tri(p-methoxyphenyl)methyl, 4-(4′-bromophenacyloxyphenyl)diphenylmethyl, 4,4′,4″-tris(4,5-dichlorophthalimidophenyl)methyl, 4,4′,4″-tris(levulinoyloxyphenyl)methyl, 4,4′,4″-tris(benzoyloxyphenyl)methyl, 3-(imidazol-1-yl)bis(4′,4″-dimethoxyphenyl)methyl, 1,1-bis(4-methoxyphenyl)-1′-pyrenylmethyl, 9-anthryl, 9-(9-phenyl)xanthenyl, 9-(9-phenyl-10-oxo)anthryl, 1,3-benzodithiolan-2-yl, benzisothiazolyl S,S-dioxido, trimethylsilyl (TMS), triethylsilyl (TES), triisopropylsilyl (TIPS), dimethylisopropylsilyl (IPDMS), diethylisopropylsilyl (DEIPS), dimethylthexylsilyl, t-butyldimethylsilyl (TBDMS), t-butyldiphenylsilyl (TBDPS), tribenzylsilyl, tri-p-xylylsilyl, triphenylsilyl, diphenylmethylsilyl (DPMS), t-butylmethoxyphenylsilyl (TBMPS), formate, benzoylformate, acetate, chloroacetate, dichloroacetate, trichloroacetate, trifluoroacetate, methoxyacetate, triphenylmethoxyacetate, phenoxyacetate, p-chlorophenoxyacetate, 3-phenylpropionate, 4-oxopentanoate (levulinate), 4,4-(ethylenedithio)pentanoate (levulinoyldithioacetal), pivaloate, adamantoate, crotonate, 4-methoxycrotonate, benzoate, p-phenylbenzoate, 2,4,6-trimethylbenzoate (mesitoate), alkyl methyl carbonate, 9-fluorenylmethyl carbonate (Fmoc), alkyl ethyl carbonate, alkyl 2,2,2-trichloroethyl carbonate (Troc), 2-(trimethylsilyl)ethyl carbonate (TMSEC), 2-(phenylsulfonyl)ethyl carbonate (Psec), 2-(triphenylphosphonio)ethyl carbonate (Peoc), alkyl isobutyl carbonate, alkyl vinyl carbonate alkyl allyl carbonate, alkyl p-nitrophenyl carbonate, alkyl benzyl carbonate, alkyl p-methoxybenzyl carbonate, alkyl 3,4-dimethoxybenzyl carbonate, alkyl o-nitrobenzyl carbonate, alkyl p-nitrobenzyl carbonate, alkyl S-benzyl thiocarbonate, 4-ethoxy-1-napththyl carbonate, methyl dithiocarbonate, 2-iodobenzoate, 4-azidobutyrate, 4-nitro-4-methylpentanoate, o-(dibromomethyl)benzoate, 2-formylbenzenesulfonate, 2-(methylthiomethoxy)ethyl, 4-(methylthiomethoxy)butyrate, 2-(methylthiomethoxymethyl)benzoate, 2,6-dichloro-4-methylphenoxyacetate, 2,6-dichloro-4-(1,1,3,3-tetramethylbutyl)phenoxyacetate, 2,4-bis(1,1-dimethylpropyl)phenoxyacetate, chlorodiphenylacetate, isobutyrate, monosuccinoate, (E)-2-methyl-2-butenoate, o-(methoxycarbonyl)benzoate, α-naphthoate, nitrate, alkyl N,N′,N′-tetramethylphosphorodiamidate, alkyl N-phenylcarbamate, borate, dimethylphosphinothioyl, alkyl 2,4-dinitrophenylsulfenate, sulfate, methanesulfonate (mesylate), benzylsulfonate, and tosylate (Ts). For protecting 1,2- or 1,3-diols, the protecting groups include methylene acetal, ethylidene acetal, 1-t-butylethylidene ketal, 1-phenylethylidene ketal, (4-methoxyphenyl)ethylidene acetal, 2,2,2-trichloroethylidene acetal, acetonide, cyclopentylidene ketal, cyclohexylidene ketal, cycloheptylidene ketal, benzylidene acetal, p-methoxybenzylidene acetal, 2,4-dimethoxybenzylidene ketal, 3,4-dimethoxybenzylidene acetal, 2-nitrobenzylidene acetal, methoxymethylene acetal, ethoxymethylene acetal, dimethoxymethylene ortho ester, 1-methoxyethylidene ortho ester, 1-ethoxyethylidine ortho ester, 1,2-dimethoxyethylidene ortho ester, α-methoxybenzylidene ortho ester, 1-(N,N-dimethylamino)ethylidene derivative, α-(N,N′-dimethylamino)benzylidene derivative, 2-oxacyclopentylidene ortho ester, di-t-butylsilylene group (DTBS), 1,3-(1,1,3,3-tetraisopropyldisiloxanylidene) derivative (TIPDS), tetra-t-butoxydisiloxane-1,3-diylidene derivative (TBDS), cyclic carbonates, cyclic boronates, ethyl boronate, and phenyl boronate. Amino-protecting groups include methyl carbamate, ethyl carbamante, 9-fluorenylmethyl carbamate (Fmoc), 9-(2-sulfo)fluorenylmethyl carbamate, 9-(2,7-dibromo)fluoroenylmethyl carbamate, 2,7-di-t-butyl-[9-(10,10-dioxo-10,10,10,10-tetrahydrothioxanthyl)]methyl carbamate (DBD-Tmoc), 4-methoxyphenacyl carbamate (Phenoc), 2,2,2-trichloroethyl carbamate (Troc), 2-trimethylsilylethyl carbamate (Teoc), 2-phenylethyl carbamate (hZ), 1-(1-adamantyl)-1-methylethyl carbamate (Adpoc), 1,1-dimethyl-2-haloethyl carbamate, 1,1-dimethyl-2,2-dibromoethyl carbamate (DB-t-BOC), 1,1-dimethyl-2,2,2-trichloroethyl carbamate (TCBOC), 1-methyl-1-(4-biphenylyl)ethyl carbamate (Bpoc), 1-(3,5-di-t-butylphenyl)-1-methylethyl carbamate (t-Bumeoc), 2-(2′- and 4′-pyridyl)ethyl carbamate (Pyoc), 2-(N,N-dicyclohexylcarboxamido)ethyl carbamate, t-butyl carbamate (BOC), 1-adamantyl carbamate (Adoc), vinyl carbamate (Voc), allyl carbamate (Alloc), 1-isopropylallyl carbamate (Ipaoc), cinnamyl carbamate (Coc), 4-nitrocinnamyl carbamate (Noc), 8-quinolyl carbamate, N-hydroxypiperidinyl carbamate, alkyldithio carbamate, benzyl carbamate (Cbz), p-methoxybenzyl carbamate (Moz), p-nitobenzyl carbamate, p-bromobenzyl carbamate, p-chlorobenzyl carbamate, 2,4-dichlorobenzyl carbamate, 4-methylsulfinylbenzyl carbamate (Msz), 9-anthrylmethyl carbamate, diphenylmethyl carbamate, 2-methylthioethyl carbamate, 2-methylsulfonylethyl carbamate, 2-(p-toluenesulfonyl)ethyl carbamate, [2-(1,3-dithianyl)]methyl carbamate (Dmoc), 4-methylthiophenyl carbamate (Mtpc), 2,4-dimethylthiophenyl carbamate (Bmpc), 2-phosphonioethyl carbamate (Peoc), 2-triphenylphosphonioisopropyl carbamate (Ppoc), 1,1-dimethyl-2-cyanoethyl carbamate, m-chloro-p-acyloxybenzyl carbamate, p-(dihydroxyboryl)benzyl carbamate, 5-benzisoxazolylmethyl carbamate, 2-(trifluoromethyl)-6-chromonylmethyl carbamate (Tcroc), m-nitrophenyl carbamate, 3,5-dimethoxybenzyl carbamate, o-nitrobenzyl carbamate, 3,4-dimethoxy-6-nitrobenzyl carbamate, phenyl(o-nitrophenyl)methyl carbamate, phenothiazinyl-(10)-carbonyl derivative, N′-p-toluenesulfonylaminocarbonyl derivative, N′-phenylaminothiocarbonyl derivative, t-amyl carbamate, S-benzyl thiocarbamate, p-cyanobenzyl carbamate, cyclobutyl carbamate, cyclohexyl carbamate, cyclopentyl carbamate, cyclopropylmethyl carbamate, p-decyloxybenzyl carbamate, 2,2-dimethoxycarbonylvinyl carbamate, o-(N,N-dimethylcarboxamido)benzyl carbamate, 1,1-dimethyl-3-(N,N-dimethylcarboxamido)propyl carbamate, 1,1-dimethylpropynyl carbamate, di(2-pyridyl)methyl carbamate, 2-furanylmethyl carbamate, 2-iodoethyl carbamate, isoborynl carbamate, isobutyl carbamate, isonicotinyl carbamate, p-(p′-methoxyphenylazo)benzyl carbamate, 1-methylcyclobutyl carbamate, 1-methylcyclohexyl carbamate, 1-methyl-1-cyclopropylmethyl carbamate, 1-methyl-1-(3,5-dimethoxyphenyl)ethyl carbamate, 1-methyl-1-(p-phenylazophenyl)ethyl carbamate, 1-methyl-1-phenylethyl carbamate, 1-methyl-1-(4-pyridyl)ethyl carbamate, phenyl carbamate, p-(phenylazo)benzyl carbamate, 2,4,6-tri-t-butylphenyl carbamate, 4-(trimethylammonium)benzyl carbamate, 2,4,6-trimethylbenzyl carbamate, formamide, acetamide, chloroacetamide, trichloroacetamide, trifluoroacetamide, phenylacetamide, 3-phenylpropanamide, picolinamide, 3-pyridylcarboxamide, N-benzoylphenylalanyl derivative, benzamide, p-phenylbenzamide, o-nitophenylacetamide, o-nitrophenoxyacetamide, acetoacetamide, (N′-dithiobenzyloxycarbonylamino)acetamide, 3-(p-hydroxyphenyl)propanamide, 3-(o-nitrophenyl)propanamide, 2-methyl-2-(o-nitrophenoxy)propanamide, 2-methyl-2-(o-phenylazophenoxy)propanamide, 4-chlorobutanamide, 3-methyl-3-nitrobutanamide, o-nitrocinnamide, N-acetylmethionine derivative, o-nitrobenzamide, o-(benzoyloxymethyl)benzamide, 4,5-diphenyl-3-oxazolin-2-one, N-phthalimide, N-dithiasuccinimide (Dts), N-2,3-diphenylmaleimide, N-2,5-dimethylpyrrole, N-1,1,4,4-tetramethyldisilylazacyclopentane adduct (STABASE), 5-substituted 1,3-dimethyl-1,3,5-triazacyclohexan-2-one, 5-substituted 1,3-dibenzyl-1,3,5-triazacyclohexan-2-one, 1-substituted 3,5-dinitro-4-pyridone, N-methylamine, N-allylamine, N-[2-(trimethylsilyl)ethoxy]methylamine (SEM), N-3-acetoxypropylamine, N-(1-isopropyl-4-nitro-2-oxo-3-pyroolin-3-yl)amine, quaternary ammonium salts, N-benzylamine, N-di(4-methoxyphenyl)methylamine, N-5-dibenzosuberylamine, N-triphenylmethylamine (Tr), N-[(4-methoxyphenyl)diphenylmethyl]amine (MMTr), N-9-phenylfluorenylamine (PhF), N-2,7-dichloro-9-fluorenylmethyleneamine, N-ferrocenylmethylamino (Fcm), N-2-picolylamino N′-oxide, N-1,1-dimethylthiomethyleneamine, N-benzylideneamine, N-p-methoxybenzylideneamine, N-diphenylmethyleneamine, N-[(2-pyridyl)mesityl]methyleneamine, N—(N′,N′-dimethylaminomethylene)amine, N,N′-isopropylidenediamine, N-p-nitrobenzylideneamine, N-salicylideneamine, N-5-chlorosalicylideneamine, N-(5-chloro-2-hydroxyphenyl)phenylmethyleneamine, N-cyclohexylideneamine, N-(5,5-dimethyl-3-oxo-1-cyclohexenyl)amine, N-borane derivative, N-diphenylborinic acid derivative, N-[phenyl(pentacarbonylchromium- or tungsten)carbonyl]amine, N-copper chelate, N-zinc chelate, N-nitroamine, N-nitrosoamine, amine N-oxide, diphenylphosphinamide (Dpp), dimethylthiophosphinamide (Mpt), diphenylthiophosphinamide (Ppt), dialkyl phosphoramidates, dibenzyl phosphoramidate, diphenyl phosphoramidate, benzenesulfenamide, o-nitrobenzenesulfenamide (Nps), 2,4-dinitrobenzenesulfenamide, pentachlorobenzenesulfenamide, 2-nitro-4-methoxybenzenesulfenamide, triphenylmethylsulfenamide, 3-nitropyridinesulfenamide (Npys), p-toluenesulfonamide (Ts), benzenesulfonamide, 2,3,6,-trimethyl-4-methoxybenzenesulfonamide (Mtr), 2,4,6-trimethoxybenzenesulfonamide (Mtb), 2,6-dimethyl-4-methoxybenzenesulfonamide (Pme), 2,3,5,6-tetramethyl-4-methoxybenzenesulfonamide (Mte), 4-methoxybenzenesulfonamide (Mbs), 2,4,6-trimethylbenzenesulfonamide (Mts), 2,6-dimethoxy-4-methylbenzenesulfonamide (iMds), 2,2,5,7,8-pentamethylchroman-6-sulfonamide (Pmc), methanesulfonamide (Ms), 3-trimethylsilylethanesulfonamide (SES), 9-anthracenesulfonamide, 4-(4′,8′-dimethoxynaphthylmethyl)benzenesulfonamide (DNMBS), benzylsulfonamide, trifluoromethylsulfonamide, and phenacylsulfonamide.

Exemplary protecting groups are detailed herein, however, it will be appreciated that the present invention is not intended to be limited to these protecting groups; rather, a variety of additional equivalent protecting groups can be readily identified using the above criteria and utilized in the method of the present invention. Additionally, a variety of protecting groups are described in Protecting Groups in Organic Synthesis, T. W. Greene and P. G. M. Wuts, 3^(rd) edition, John Wiley & Sons, 1999, the entirety of which is incorporated herein by reference.

When substituents are described herein, the term “radical” or “optionally substituted radical” is sometimes used. In this context, “radical” means a moiety or functional group having an available position for attachment to the structure on which the substituent is bound. In general the point of attachment would bear a hydrogen atom if the substituent were an independent neutral molecule rather than a substituent. The terms “radical” or “optionally-substituted radical” in this context are thus interchangeable with “group” or “optionally-substituted group”.

As described herein, compounds of the invention may contain “optionally substituted” moieties. In general, the term “substituted”, whether preceded by the term “optionally” or not, means that one or more hydrogens of the designated moiety are replaced with a suitable substituent. Unless otherwise indicated, an “optionally substituted group” or “optionally substituted radical” may have a suitable substituent at each substitutable position of the group, and when more than one position in any given structure may be substituted with more than one substituent selected from a specified group, the substituent may be either the same or different at every position. Combinations of substituents envisioned by this invention are preferably those that result in the formation of stable or chemically feasible compounds. The term “stable”, as used herein, refers to compounds that are not substantially altered when subjected to conditions to allow for their production, detection, and, in certain embodiments, their recovery, purification, and use for one or more of the purposes disclosed herein.

In some chemical structures herein, substituents are shown attached to a bond that crosses a bond in a ring of the depicted molecule. This convention indicates that one or more of the substituents may be attached to the ring at any available position (usually in place of a hydrogen atom of the parent structure). In cases where an atom of a ring so substituted has two substitutable positions, two groups may be present on the same ring atom. Unless otherwise indicated, when more than one substituent is present, each is defined independently of the others, and each may have a different structure. In cases where the substituent shown crossing a bond of the ring is —R, this has the same meaning as if the ring were said to be “optionally substituted” as described in the preceding paragraph.

Suitable monovalent substituents on a substitutable carbon atom of an “optionally substituted” group are independently halogen; —(CH₂)₀₋₄R^(◯); —(CH₂)₀₋₄OR^(◯); —O—(CH₂)₀₋₄C(O)OR^(◯); —(CH₂)₀₋₄CH(OR^(◯))₂; —(CH₂)₀₋₄SR^(◯); —(CH₂)₀₋₄Ph, which may be substituted with R^(◯); —(CH₂)₀₋₄O(CH₂)₀₋₁Ph which may be substituted with R^(◯); —CH═CHPh, which may be substituted with R^(◯); —NO₂; —CN; —N₃; —(CH₂)₀₋₄N(R^(◯))₂; —(CH₂)₀₋₄N(R^(◯))C(O)R^(◯); —N(R^(◯))C(S)R^(◯); —(CH₂)₀₋₄N(R^(◯))C(O)NR^(◯) ₂; —N(R^(◯))C(S)NR^(◯) ₂; —(CH₂)₄N(R^(◯))C(O)OR^(◯); —N(R^(◯))N(R^(◯))C(O)R^(◯); —N(R^(◯))N(R^(◯))C(O)NR^(◯) ₂; —N(R^(◯))N(R^(◯))C(O)OR^(◯); —(CH₂)₀₋₄C(O)R^(◯); —C(S)R^(◯); —(CH₂)₀₋₄C(O)OR^(◯); —(CH₂)₀₋₄C(O)N(R^(◯))₂; —(CH₂)₀₋₄C(O)SR^(◯); —(CH₂)₀₋₄C(O)OSiR^(◯) ₃; —(CH₂)₀₋₄C(O)R^(◯); —OC(O)(CH₂)₀₋₄SR—, SC(S)SR^(◯); —(CH₂)₀₋₄SC(O)R^(◯); —(CH₂)₀₋₄C(O)NR^(◯) ₂; —C(S)NR^(◯) ₂; —C(S)SR^(◯); —SC(S)SR^(◯), —(CH₂)₀₋₄OC(O)NR₂; —C(O)N(OR^(◯))R^(◯); —C(O)C(O)R^(◯); —C(O)CH₂C(O)R^(◯); —C(NOR^(◯))R^(◯); —(CH₂)₀₋₄SSR^(◯); —(CH₂)₀₋₄S(O)₂R^(◯); —(CH₂)₀₋₄S(O)₂OR^(◯); —(CH₂)₀₋₄OS(O)₂R^(◯); —S(O)₂NR₂; —(CH₂)₀₋₄S(O)R^(◯); —N(R^(◯))S(O)₂NR₂; —N(R^(◯))S(O)₂R^(◯); —N(OR^(◯))R^(◯); —C(NH)NR₂; —P(O)₂R^(◯); —P(O)R₂; —OP(O)R₂; —OP(OXOR^(◯))₂; SiR^(◯) ₃; —(C₁₋₄ straight or branched alkylene)O—N(R^(◯))₂; or —(C₁₋₄ straight or branched alkylene)C(O)O—N(R^(◯))₂, wherein each R^(◯) may be substituted as defined below and is independently hydrogen, C₁₋₈ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R^(◯), taken together with intervening atom(s), form a 3-12-membered saturated, partially unsaturated, or aryl mono- or polycyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, which may be substituted as defined below.

Suitable monovalent substituents on R^(◯) (or the ring formed by taking two independent occurrences of R^(◯) together with their intervening atoms), are independently halogen, —(CH₂)₀₋₂R^(), -(haloR^()), —(CH₂)₀₋₂OH, —(CH₂)₀₋₂OR^(), —(CH₂)₀₋₂CH(OR^())₂; —O(haloR^()), —CN, —N₃, —(CH₂)₀₋₂C(O)R^(), —(CH₂)₀₋₂C(O)OH, —(CH₂)₀₋₂C(O)OR^(), —(CH₂)₀₋₄C(O)N(R^())₂; —(CH₂)₀₋₂SR^(), —(CH₂)₀₋₂SH, —(CH₂)₀₋₂NH₂, —(CH₂)₀₋₂NHR^(), —(CH₂)₀₋₂NR^() ₂, —NO₂, —SiR^() ₃, —OSiR^() ₃, —C(O)SR^(), —(C₁₋₄ straight or branched alkylene)C(O)OR^(), or —SSR^() wherein each R^() is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently selected from C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents on a saturated carbon atom of R^(◯) include ═O and ═S.

Suitable divalent substituents on a saturated carbon atom of an “optionally substituted” group include the following: ═O, ═S, ═NNR*2, ═NNHC(O)R*, ═NNHC(O)OR*, ═NNHS(O)₂R*, ═NR*, ═NOR*, —O(C(R*₂))₂₋₃O—, or —S(C(R*₂))₂₋₃S—, wherein each independent occurrence of R* is selected from hydrogen, C₁₋₆ aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. Suitable divalent substituents that are bound to vicinal substitutable carbons of an “optionally substituted” group include: —O(CR*₂)₂₋₃O—, wherein each independent occurrence of R* is selected from hydrogen, C₁₋₆ aliphatic which may be substituted as defined below, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on the aliphatic group of R* include halogen, —R^(), -(haloR^()), —OH, —OR^(), —O(haloR^()), —CN, —C(O)OH, —C(O)OR^(), —NH₂, —NHR^(), —NR^() ₂, or —NO₂, wherein each R^() is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

Suitable substituents on a substitutable nitrogen of an “optionally substituted” group include —R^(†), —NR^(†) ₂, —C(O)R^(†), —C(O)OR^(†), —C(O)C(O)R^(†), —C(O)CH₂C(O)R^(†), —S(O)₂R^(†), —S(O)₂NR^(†) ₂, —C(S)NR^(†) ₂, —C(NH)NR^(†) ₂, or —N(R^(†))S(O)₂R^(†); wherein each R^(†) is independently hydrogen, C₁₋₆ aliphatic which may be substituted as defined below, unsubstituted —OPh, or an unsubstituted 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, or, notwithstanding the definition above, two independent occurrences of R^(†), taken together with intervening atom(s) form an unsubstituted 3-12-membered saturated, partially unsaturated, or aryl mono- or bicyclic ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur. A substitutable nitrogen may be substituted with three R^(†) substituents to provide a charged ammonium moiety —N⁺(R^(†))₃, wherein the ammonium moiety is further complexed with a suitable counterion.

Suitable substituents on the aliphatic group of R^(†) are independently halogen, —R^(), -(haloR^()), —OH, —OR^(), —O(haloR^()), —CN, —C(O)OH, —C(O)OR^(), —NH₂, —NHR^(), —NR^() ₂, or —NO₂, wherein each R^() is unsubstituted or where preceded by “halo” is substituted only with one or more halogens, and is independently C₁₋₄ aliphatic, —CH₂Ph, —O(CH₂)₀₋₁Ph, or a 5-6-membered saturated, partially unsaturated, or aryl ring having 0-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur.

As used herein, the term “catalyst” refers to a substance the presence of which increases the rate and/or extent of a chemical reaction, while not being consumed or undergoing a permanent chemical change itself.

As used herein, the term “multidentate” refers to ligands having multiple sites capable of coordinating to a single metal center.

As used herein, the term “activating moiety” refers to a moiety comprising one or more activating functional groups. In certain embodiments, an activating moiety improves the catalytic activity of a metal complex. In some embodiments, such improved catalytic activity is characterized by higher conversion of starting materials compared to a metal complex lacking an activating moiety. In some embodiments, such improved catalytic activity is characterized by higher rate of conversion of starting materials compared to a metal complex lacking an activating moiety. In some embodiments, such improved catalytic activity is characterized by higher yield of product compared to a metal complex lacking an activating moiety.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

The present invention encompasses the recognition that there remains a need for metal complexes useful in the copolymerization of epoxides and carbon dioxide. Metal complexes provided by the present invention can show significant advantages for uses in the copolymerization of epoxides and carbon dioxide. While not wishing to be bound by any particular theory, it is believed that metal complexes of the present invention provide enhanced reactivity and/or selectivity when compared to known metal complexes. In certain embodiments, a provided metal complex is highly selective for a copolymerization reaction, resulting in little or no cyclic carbonate formation. In certain embodiments, a provided metal complex is highly selective for polycarbonate formation.

The present invention provides, among other things, metal complexes for the copolymerization of carbon dioxide and epoxides and methods of using the same. In certain embodiments, provided metal complexes contain two or more metal atoms. In certain embodiments, the metal atoms are complexed to one or more multidentate ligands and at least one tethered activating moiety tethered to one or more of the ligands. In some embodiments, an activating moiety comprises a linker and one or more activating functional groups. In certain embodiments, at least one activating functional group present on the tethered moiety can act as a polymerization co-catalyst and thereby increase the rate of the copolymerization. In some embodiments, provided metal complexes act as polymerization catalysts.

In certain embodiments, the present invention provides multi-metal complexes and methods for using the same in the copolymerization of carbon dioxide and epoxides.

In some embodiments, provided metal complexes have a structure C-1:

wherein:

-   -   M¹ is a first metal atom;     -   M² is a second metal atom;

comprises a multidentate ligand system capable of coordinating both metal atoms;

-   -   represents one or more activating moieties attached to the         multidentate ligand system, where         is a linker moiety covalently coupled to the ligand system, each         Z is an activating functional group; and m is an integer from 1         to 4 representing the number of Z groups present on an         individual linker moiety.

II. Linker Moieties

In certain embodiments, each activating moiety

comprises a linker “

” coupled to at least one activating functional group Z as described above, with m denoting the number of activating functional groups present on a single linker moiety.

In some embodiments, there may be one or more activating moieties

tethered to a given metal complex; similarly, each activating moiety itself may contain more than one activating functional group Z. In certain embodiments, each activating moiety contains only one activating functional group (i.e. m=1). In some embodiments, each activating moiety contains more than one activating functional groups (i.e. m>1). In certain embodiments, an activating moiety contains two activating functional groups (i.e. m=2). In certain embodiments, an activating moiety contains three activating functional groups (i.e. m=3). In certain embodiments, an activating moiety contains four activating functional groups (i.e. m=4). In certain embodiments where more than one activating functional group is present on an activating moiety, the activating functional groups are the same. In some embodiments where more than one activating functional group is present on an activating moiety, two or more of the activating functional groups are different.

In certain embodiments, each linker moiety

contains 1-30 atoms including at least one carbon atom, and optionally one or more atoms selected from the group consisting of N, O, S, Si, B, and P.

In certain embodiments, a linker is an optionally substituted C₂₋₃₀ aliphatic group wherein one or more methylene units are optionally and independently replaced by -Cy-, —NR^(y)—, —N(R^(y))C(O)—, —C(O)N(R^(y))—, —O—, —C(O)—, —OC(O)—, —C(O)O—, —S—, —SO—, —SO₂—, —C(═S)—, —C(═NR^(y))—, or —N═N—, wherein:

-   -   each -Cy- is independently an optionally substituted 5-8         membered bivalent, saturated, partially unsaturated, or aryl         ring having 0-4 heteroatoms independently selected from         nitrogen, oxygen, or sulfur, or an optionally substituted 8-10         membered bivalent saturated, partially unsaturated, or aryl         bicyclic ring having 0-5 heteroatoms independently selected from         nitrogen, oxygen, or sulfur; and     -   each R^(y) is independently —H, or an optionally substituted         radical selected from the group consisting of C₁₋₆ aliphatic,         phenyl, a 3-7 membered saturated or partially unsaturated         carbocyclic ring, a 3-7 membered saturated or partially         unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms         independently selected from nitrogen, oxygen, or sulfur, a 5-6         membered heteroaryl ring having 1-3 heteroatoms independently         selected from nitrogen, oxygen, or sulfur, and 8- to 10-membered         aryl.

In certain embodiments, a linker moiety is a C₄-C₁₂ aliphatic group substituted with one or more moieties selected from the group consisting of halogen, —NO₂, —CN, —SR, —S(O)R^(y), —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO, —N₃, —OR⁴, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y), and —NR^(y)C(O)OR^(y), where each R^(y) and R⁴ is independently as defined above and described in classes and subclasses herein.

In certain embodiments, a linker moiety is an optionally substituted C₃-C₃₀ aliphatic group. In certain embodiments, a linker is an optionally substituted C₄₋₂₄ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₄-C₂₀ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₄-C₁₂ aliphatic group. In certain embodiments, a linker is an optionally substituted C₄₋₁₀ aliphatic group. In certain embodiments, a linker is an optionally substituted C₄₋₈ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₄-C₆ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₆-C₁₂ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₈ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₇ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₆ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₅ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₄ aliphatic group. In certain embodiments, a linker moiety is an optionally substituted C₃ aliphatic group. In certain embodiments, a aliphatic group in the linker moiety is an optionally substituted straight alkyl chain. In certain embodiments, the aliphatic group is an optionally substituted branched alkyl chain. In some embodiments, a linker moiety is a C₄ to C₂₀ alkyl group having one or more methylene groups replaced by —C(R^(◯))₂— wherein R^(◯) is as defined above. In certain embodiments, a linker moiety consists of a bivalent aliphatic group having 4 to 30 carbons including one or more C₁₋₄ alkyl substituted carbon atoms. In certain embodiments, a linker moiety consists of a bivalent aliphatic group having 4 to 30 carbons including one or more gem-dimethyl substituted carbon atoms.

In certain embodiments, a linker moiety includes one or more optionally substituted cyclic elements selected from the group consisting of saturated or partially unsaturated carbocyclic, aryl, heterocyclic, or heteroaryl. In certain embodiments, a linker moiety consists of the substituted cyclic element, in some embodiments the cyclic element is part of a linker with one or more non-ring heteroatoms or optionally substituted aliphatic groups comprising other parts of the linker moiety.

In some embodiments, a linker moiety is of sufficient length to allow one or more activating functional groups to be positioned near a metal atom of a metal complex. In certain embodiments, structural constraints are built into a linker moiety to control the disposition and orientation of one or more activating functional groups near a metal center of a metal complex. In certain embodiments, such structural constraints are selected from the group consisting of cyclic moieties, bicyclic moieties, bridged cyclic moieties and tricyclic moieties. In some embodiments, such structural constraints are the result of acyclic steric interactions. In certain embodiments, steric interactions due to syn-pentane, gauche-butane, and/or allylic strain in a linker moiety, bring about structural constraints that affect the orientation of a linker and one or more activating groups. In certain embodiments, structural constraints are selected from the group consisting of cis double bonds, trans double bonds, cis allenes, trans allenes, and triple bonds. In some embodiments, structural constraints are selected from the group consisting of substituted carbons including geminally disubstituted groups such as sprirocyclic rings, gem dimethyl groups, gem diethyl groups and gem diphenyl groups. In certain embodiments, structural constraints are selected from the group consisting of heteratom-containing functional groups such as sulfoxides, amides, and oximes.

In certain embodiments, linker moieties are selected from the group consisting of:

wherein each s is independently 0-6, t is 0-4, R^(y) as defined above and described in classes and subclasses herein, * represents the site of attachment to a ligand, and each # represents a site of attachment of an activating functional group.

In some embodiments, s is 0. In some embodiments, s is 1. In some embodiments, s is 2. In some embodiments, s is 3. In some embodiments, s is 4. In some embodiments, s is 5. In some embodiments, s is 6.

In some embodiments, t is 1. In some embodiments, t is 2. In some embodiments, t is 3. In some embodiments, t is 4.

II. Activating Functional Groups

In some embodiments, an activating functional group is selected from the group consisting of neutral nitrogen-containing functional groups, cationic moieties, phosphorous-containing functional groups, and combinations of two or more of these.

II.a. Neutral Nitrogen-Containing Activating Groups

In some embodiments, one or more tethered activating functional groups on provided metal complexes are neutral nitrogen-containing moieties. In some embodiments, such moieties include one or more of the structures in Table Z-1:

TABLE Z-1

or a combination of two or more of these,

wherein:

-   -   each R¹ and R² is independently hydrogen or an optionally         substituted radical selected from the group consisting of C₁₋₂₀         aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated         or partially unsaturated monocyclic carbocycle; a 7- to         14-membered saturated or partially unsaturated polycyclic         carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having         1-4 heteroatoms independently selected from nitrogen, oxygen, or         sulfur; an 8- to 14-membered polycyclic heteroaryl ring having         1-5 heteroatoms independently selected from nitrogen, oxygen, or         sulfur; a 3- to 8-membered saturated or partially unsaturated         monocyclic heterocyclic ring having 1-3 heteroatoms         independently selected from nitrogen, oxygen, or sulfur; a 6- to         14-membered saturated or partially unsaturated polycyclic         heterocycle having 1-5 heteroatoms independently selected from         nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered         polycyclic aryl ring; wherein R¹ and R² can be taken together         with intervening atoms to form one or more optionally         substituted rings optionally containing one or more additional         heteroatoms;     -   each R³ is independently hydrogen or an optionally substituted         radical selected from the group consisting of C₁₋₂₀ aliphatic;         C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially         unsaturated monocyclic carbocycle; a 7- to 14-membered saturated         or partially unsaturated polycyclic carbocycle; a 5- to         6-membered monocyclic heteroaryl ring having 1-4 heteroatoms         independently selected from nitrogen, oxygen, or sulfur; an 8-         to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms         independently selected from nitrogen, oxygen, or sulfur, a 3- to         8-membered saturated or partially unsaturated monocyclic         heterocyclic ring having 1-3 heteroatoms independently selected         from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated         or partially unsaturated polycyclic heterocycle having 1-5         heteroatoms independently selected from nitrogen, oxygen, or         sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring;         wherein an R³ group can be taken with an R¹ or R² group to form         one or more optionally substituted rings; and     -   each R⁴ is independently hydrogen, a hydroxyl protecting group,         or an optionally substituted radical selected from the group         consisting of C₁₋₂₀ acyl; C₁₋₂₀ aliphatic; C₁₋₂₀         heteroaliphatic; a 3- to 8-membered saturated or partially         unsaturated monocyclic carbocycle; a 7- to 14-membered saturated         or partially unsaturated polycyclic carbocycle; a 5- to         6-membered monocyclic heteroaryl ring having 1-4 heteroatoms         independently selected from nitrogen, oxygen, or sulfur, an 8-         to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms         independently selected from nitrogen, oxygen, or sulfur; a 3- to         8-membered saturated or partially unsaturated monocyclic         heterocyclic ring having 1-3 heteroatoms independently selected         from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated         or partially unsaturated polycyclic heterocycle having 1-5         heteroatoms independently selected from nitrogen, oxygen, or         sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring.

In certain embodiments, each R¹ group is the same. In other embodiments, R¹ groups are different. In certain embodiments, R¹ is hydrogen. In some embodiments, R¹ is an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to 14-membered heteroaryl, phenyl, 8- to 10-membered aryl and 3- to 7-membered heterocyclic. In some embodiments, R¹ is an optionally substituted radical selected from the group consisting of a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring.

In certain embodiments, R¹ is an optionally substituted radical selected from the group consisting of C₁₋₁₂ aliphatic and C₁₋₁₂ heteroaliphatic. In some embodiments, R¹ is optionally substituted C₁₋₂₀ aliphatic. In some embodiments, R¹ is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R¹ is optionally substituted C₁₋₆ aliphatic. In some embodiments, R¹ is optionally substituted C₁₋₂₀ heteroaliphatic. In some embodiments, R¹ is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, R¹ is optionally substituted phenyl. In some embodiments, R¹ is optionally substituted 8- to 10-membered aryl. In some embodiments, R¹ is an optionally substituted 5- to 6-membered heteroaryl group. In some embodiments, R¹ is an optionally substituted 8- to 14-membered polycyclic heteroaryl group. In some embodiments, R¹ is optionally substituted 3- to 8-membered heterocyclic.

In certain embodiments, each R¹ is independently hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionally substituted phenyl, or optionally substituted benzyl. In certain embodiments, R¹ is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R¹ is butyl. In some embodiments, R¹ is isopropyl. In some embodiments, R¹ is neopentyl. In some embodiments, R¹ is perfluoro. In some embodiments, R¹ is —CF₂CF₃. In some embodiments, R¹ is phenyl. In some embodiments, R¹ is benzyl.

In certain embodiments, each R² group is the same. In other embodiments, R² groups are different. In certain embodiments, R² is hydrogen. In some embodiments, R² is an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to 14-membered heteroaryl, phenyl, 8- to 10-membered aryl and 3- to 7-membered heterocyclic. In some embodiments, R² is an optionally substituted radical selected from the group consisting of a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring.

In certain embodiments, R² is an optionally substituted radical selected from the group consisting of C₁₋₁₂ aliphatic and C₁₋₁₂ heteroaliphatic. In some embodiments, R² is optionally substituted C₁₋₂₀ aliphatic. In some embodiments, R² is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R² is optionally substituted C₁₋₆ aliphatic. In some embodiments, R² is optionally substituted C₁₋₂₀ heteroaliphatic. In some embodiments, R² is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, R² is optionally substituted phenyl. In some embodiments, R² is optionally substituted 8- to 10-membered aryl. In some embodiments, R² is an optionally substituted 5- to 6-membered heteroaryl group. In some embodiments, R² is an optionally substituted 8- to 14-membered polycyclic heteroaryl group. In some embodiments, R² is optionally substituted 3- to 8-membered heterocyclic.

In certain embodiments, each R² is independently hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionally substituted phenyl, or optionally substituted benzyl. In certain embodiments, R² is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R² is butyl. In some embodiments, R² is isopropyl. In some embodiments, R² is neopentyl. In some embodiments, R² is perfluoro. In some embodiments, R² is —CF₂CF₃. In some embodiments, R² is phenyl. In some embodiments, R² is benzyl.

In certain embodiments, each R¹ and R² are hydrogen. In some embodiments, each R¹ is hydrogen each and each R² is other than hydrogen. In some embodiments, each R² is hydrogen each and each R¹ is other than hydrogen.

In certain embodiments, R¹ and R² are both methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R¹ and R² are each butyl. In some embodiments, R¹ and R² are each isopropyl. In some embodiments, R¹ and R² are each perfluoro. In some embodiments, R¹ and R² are —CF₂CF₃. In some embodiments, R¹ and R² are each phenyl. In some embodiments, R¹ and R² are each benzyl.

In some embodiments, R¹ and R² are taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings. In certain embodiments, R¹ and R² are taken together to form a ring fragment selected from the group consisting of: —C(R^(y))₂—, —C(R^(y))₂C(R^(y))₂—, —C(R^(y))₂C(R^(y))₂C(R^(y))₂—, —C(R^(y))₂OC(R^(y))₂—, and —C(R^(y))₂NR^(y)C(R^(y))₂—, wherein R^(y) is as defined above. In certain embodiments, R¹ and R² are taken together to form a ring fragment selected from the group consisting of: —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH₂OCH₂—, and —CH₂NR^(y)CH₂—. In some embodiments, R¹ and R² are taken together to form an unsaturated linker moiety optionally containing one or more additional heteroatoms. In some embodiments, the resulting nitrogen-containing ring is partially unsaturated. In certain embodiments, the resulting nitrogen-containing ring comprises a fused polycyclic heterocycle.

In certain embodiments, R³ is H. In certain embodiments, R³ is optionally C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic, 5- to 14-membered heteroaryl, phenyl, 8- to 10-membered aryl or 3- to 7-membered heterocyclic. In some embodiments, R³ is an optionally substituted radical selected from the group consisting of a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring. In certain embodiments, R³ is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R³ is optionally substituted C₁₋₆ aliphatic. In certain embodiments, R³ is optionally substituted phenyl.

In certain embodiments, R³ is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, phenyl or benzyl. In some embodiments, R³ is butyl. In some embodiments, R³ is isopropyl. In some embodiments, R³ is perfluoro. In some embodiments, R³ is —CF₂CF₃.

In some embodiments, one or more R¹ or R² groups are taken together with R³ and intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring. In certain embodiments, R¹ and R³ are taken together to form an optionally substituted 5- or 6-membered ring. In some embodiments, R² and R³ are taken together to form an optionally substituted 5- or 6-membered ring optionally containing one or more additional heteroatoms. In some embodiments, R¹, R² and R³ are taken together to form an optionally substituted fused ring system. In some embodiments, such rings formed by combinations of any of R¹, R² and R³ are partially unsaturated or aromatic.

In certain embodiments, R⁴ is hydrogen. In some embodiments, R⁴ is an optionally substituted radical selected from the group consisting of C₁₋₁₂ aliphatic, phenyl, 8- to 10-membered aryl, and 3- to 8-membered heterocyclic. In certain embodiments, R⁴ is a C₁₋₁₂ aliphatic. In certain embodiments, R⁴ is a C₁₋₆ aliphatic. In some embodiments, R⁴ is an optionally substituted 8- to 10-membered aryl group. In certain embodiments, R⁴ is optionally substituted C₁₋₁₂ acyl or in some embodiments, optionally substituted C₁₋₆ acyl. In certain embodiments, R⁴ is optionally substituted phenyl. In some embodiments, R⁴ is a hydroxyl protecting group. In some embodiments, R⁴ is a silyl protecting group. In some embodiments, R⁴ is methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, allyl, phenyl or benzyl.

In certain embodiments, R¹ and R⁴ are taken together with intervening atoms to form one or more optionally substituted heterocyclic or heteroaryl rings optionally containing one or more additional heteroatoms.

In some embodiments, an activating functional group is an N-linked amino group:

wherein R¹ and R² are as defined above and described in classes and subclasses herein.

In some embodiments, an N-linked amino activating functional group is selected from the group consisting of:

In some embodiments, one or more activating functional groups is an N-linked hydroxyl amine derivative:

wherein R¹ and R⁴ are as defined above and described in classes and subclasses herein.

In certain embodiments, one or more N-linked hydroxyl amine activating functional groups are selected from the group consisting of:

In some embodiments, an activating functional group in a provided metal complex is an amidine. In certain embodiments, such amidine activating functional groups are selected from:

wherein each of R¹, R², and R³ is as defined above and described in classes and subclasses herein.

In certain embodiments, an activating functional group is an N-linked amidine:

wherein each of R¹, R², and R³ is as defined above and described in classes and subclasses herein. In certain embodiments, such N-linked amidine groups are selected from the group consisting of:

In certain embodiments, activating functional groups are amidine moieties linked through the imine nitrogen:

wherein each of R¹, R², and R³ is as defined above and described in classes and subclasses herein. In certain embodiments, such imine-linked amidine activating functional groups are selected from the group consisting of:

In certain embodiments, activating functional groups are amidine moieties linked through a carbon atom:

wherein each of R¹, R², and R³ is as defined above and described in classes and subclasses herein. In certain embodiments, such carbon-linked amidine activating groups are selected from the group consisting of:

In some embodiments, one or more activating functional groups is a carbamate. In certain embodiments, a carbamate is N-linked:

wherein each of R¹ and R² is as defined above and described in classes and subclasses herein. In some embodiments, a carbamate is O-linked:

wherein each of R¹ and R² is as defined above and described in classes and subclasses herein.

In some embodiments, R² is selected from the group consisting of: methyl, t-butyl, t-amyl, benzyl, adamantyl, allyl, 4-methoxycarbonylphenyl, 2-(methylsulfonyl)ethyl, 2-(4-biphenylyl)-prop-2-yl, 2-(trimethylsilyl)ethyl, 2-bromoethyl, and 9-fluorenylmethyl.

In some embodiments, an activating functional group is a guanidine or bis-guanidine group:

wherein each R¹ and R² is as defined above and described in classes and subclasses herein.

In some embodiments, any two or more R¹ or R² groups are taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings. In certain embodiments, R¹ and R² groups are taken together to form an optionally substituted 5- or 6-membered ring. In some embodiments, three or more R¹ and/or R² groups are taken together to form an optionally substituted fused ring system.

In certain embodiments, where an activating functional group is a guanidine or bis guanidine moiety, it is selected from the group consisting of:

In some embodiments, an activating functional group is a urea:

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

In certain embodiments, activating functional groups are oxime or hydrazone groups:

wherein each of R¹, R², R³, and R⁴ is as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is an N-oxide derivative:

wherein each of R¹ and R² is as defined above and described in classes and subclasses herein.

In certain embodiments, an N-oxide activating functional group is selected from the group consisting of:

II.b. Cationic Activating Groups

In some embodiments, one or more tethered activating functional groups on provided metal complexes comprise a cationic moiety. In some embodiments, a cationic moiety is selected from a structure in Table Z-2:

TABLE Z-2

-

or a combination of two or more of these, wherein:

-   -   each of R¹, R², and R³ is independently as defined above and         described in classes and subclasses herein;     -   R⁵ is R² or hydroxyl; wherein R¹ and R⁵ can be taken together         with intervening atoms to form one or more optionally         substituted carbocyclic, heterocyclic, aryl, or heteroaryl         rings;     -   each R⁶ and R⁷ is independently hydrogen or an optionally         substituted radical selected from the group consisting of C₁₋₂₀         aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated         or partially unsaturated monocyclic carbocycle; a 7- to         14-membered saturated or partially unsaturated polycyclic         carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having         1-4 heteroatoms independently selected from nitrogen, oxygen, or         sulfur; an 8- to 14-membered polycyclic heteroaryl ring having         1-5 heteroatoms independently selected from nitrogen, oxygen, or         sulfur; a 3- to 8-membered saturated or partially unsaturated         monocyclic heterocyclic ring having 1-3 heteroatoms         independently selected from nitrogen, oxygen, or sulfur; a 6- to         14-membered saturated or partially unsaturated polycyclic         heterocycle having 1-5 heteroatoms independently selected from         nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered         polycyclic aryl ring; wherein R⁶ and R⁷ can be taken together         with intervening atoms to form one or more optionally         substituted rings optionally containing one or more heteroatoms,         and an R⁶ and R⁷ group can be taken with an R¹ or R² group to         form one or more optionally substituted rings;     -   each occurrence of R⁸ is independently selected from the group         consisting of: halogen, —NO₂, —CN, —SR^(y), —S(O)R^(y),         —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO,         —N₃, —OR⁷, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y),         —NR^(y)C(O)OR^(y); or an optionally substituted radical selected         from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀         heteroaliphatic; a 3- to 8-membered saturated or partially         unsaturated monocyclic carbocycle; a 7- to 14-membered saturated         or partially unsaturated polycyclic carbocycle; a 5- to         6-membered monocyclic heteroaryl ring having 1-4 heteroatoms         independently selected from nitrogen, oxygen, or sulfur, an 8-         to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms         independently selected from nitrogen, oxygen, or sulfur; a 3- to         8-membered saturated or partially unsaturated monocyclic         heterocyclic ring having 1-3 heteroatoms independently selected         from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated         or partially unsaturated polycyclic heterocycle having 1-5         heteroatoms independently selected from nitrogen, oxygen, or         sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring;         wherein each R^(y) is independently as defined above and         described in classes and subclasses herein, and where two or         more adjacent R⁸ groups can be taken together to form an         optionally substituted saturated, partially unsaturated, or         aromatic 5- to 12-membered ring containing 0 to 4 heteroatoms;     -   X⁻ is any anion;     -   Ring A is an optionally substituted, 5- to 10-membered         heteroaryl group; and     -   Ring B is an optionally substituted, 3- to 8-membered saturated         or partially unsaturated monocyclic heterocyclic ring having 0-2         heteroatoms in addition to the depicted ring nitrogen atom         independently selected from nitrogen, oxygen, or sulfur.

In certain embodiments, a cationic activating functional group is a protonated amine:

where each of R¹ and R² is as defined above and described in classes and subclasses herein.

In some embodiments, a protonated amine activating functional group is selected from the group consisting of:

In certain embodiments, an activating functional group is a guanidinium group:

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein. In some embodiments, each R¹ and R² is independently hydrogen or C₁₋₂₀ aliphatic. In some embodiments, each R¹ and R² is independently hydrogen or C₁₋₁₂ aliphatic. In some embodiments, each R¹ and R² is independently hydrogen or C₁₋₂₀ heteroaliphatic. In some embodiments, each R¹ and R² is independently hydrogen or phenyl. In some embodiments, each R¹ and R² is independently hydrogen or 8- to 10-membered aryl. In some embodiments, each R¹ and R² is independently hydrogen or 5- to 10-membered heteroaryl. In some embodiments, each R¹ and R² is independently hydrogen or 3- to 7-membered heterocyclic. In some embodiments, one or more of R¹ and R² is optionally substituted C₁₋₁₂ aliphatic.

In some embodiments, any two or more R¹ or R² groups are taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings. In certain embodiments, R¹ and R² groups are taken together to form an optionally substituted 5- or 6-membered ring. In some embodiments, three or more R¹ and/or R² groups are taken together to form an optionally substituted fused ring system.

In certain embodiments, a R¹ and R² group are taken together with intervening atoms to form a compound selected from:

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein, and Ring G is an optionally substituted 5- to 7-membered saturated or partially unsaturated heterocyclic ring.

It will be appreciated that when a guanidinium cation is depicted as

all such resonance forms are contemplated and encompassed by the present disclosure. For example, such groups can also be depicted as

In some embodiments, a guanidinium activating functional group is selected from the group consisting of:

In some embodiments, an activating functional group is a sulfonium group or an arsonium group:

wherein each of R¹, R², and R³ are as defined above and described in classes and subclasses herein.

In some embodiments, an arsonium activating functional group is selected from the group consisting of:

In some embodiments, an activating functional group is an optionally substituted nitrogen-containing heterocycle. In certain embodiments, the nitrogen-containing heterocycle is an aromatic heterocycle. In certain embodiments, the optionally substituted nitrogen-containing heterocycle is selected from the group consisting of: pyridine, imidazole, pyrrolidine, pyrazole, quinoline, thiazole, dithiazole, oxazole, triazole, pyrazolem, isoxazole, isothiazole, tetrazole, pyrazine, thiazine, and triazine.

In some embodiments, a nitrogen-containing heterocycle includes a quaternarized nitrogen atom. In certain embodiments, a nitrogen-containing heterocycle includes an iminium moiety such as

In certain embodiments, the optionally substituted nitrogen-containing heterocycle is selected from the group consisting of pyridinium, imidazolium, pyrrolidinium, pyrazolium, quinolinium, thiazolium, dithiazolium, oxazolium, triazolium, isoxazolium, isothiazolium, tetrazolium, pyrazinium, thiazinium, and triazinium.

In certain embodiments, a nitrogen-containing heterocycle is linked to a metal complex via a ring nitrogen atom. In some embodiments, a ring nitrogen to which the attachment is made is thereby quaternized, and in some embodiments, linkage to a metal complex takes the place of an N—H bond and the nitrogen atom thereby remains neutral.

In certain embodiments, an optionally substituted N-linked nitrogen-containing heterocycle is a pyridinium derivative. In certain embodiments, optionally substituted N-linked nitrogen-containing heterocycle is an imidazolium derivative. In certain embodiments, optionally substituted N-linked nitrogen-containing heterocycle is a thiazolium derivative. In certain embodiments, optionally substituted N-linked nitrogen-containing heterocycle is a pyridinium derivative.

In some embodiments, an activating functional group is

In certain embodiments, ring A is an optionally substituted, 5- to 10-membered heteroaryl group. In some embodiments, Ring A is an optionally substituted, 6-membered heteroaryl group. In some embodiments, Ring A is a ring of a fused heterocycle. In some embodiments, Ring A is an optionally substituted pyridyl group.

In some embodiments, when Z is

ring A is other than an imidazole, an oxazole, or a thiazole.

In some embodiments, a nitrogen-containing heterocycle activating functional group is selected from the group consisting of:

In certain embodiments, Ring B is a 5-membered saturated or partially unsaturated monocyclic heterocyclic ring. In certain embodiments, Ring B is a 6-membered saturated or partially unsaturated heterocycle. In certain embodiments, Ring B is a 7-membered saturated or partially unsaturated heterocycle. In certain embodiments, Ring B is tetrahydrofuranyl, tetrahydrothienyl, pyrrolidinyl, pyrrolidonyl, piperidinyl, pyrrolinyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, decahydroquinolinyl, oxazolidinyl, piperazinyl, dioxanyl, dioxolanyl, diazepinyl, oxazepinyl, thiazepinyl, morpholinyl, and quinuclidinyl. In some embodiments, Ring B is piperidinyl.

In some embodiments, an activating functional group is

where each R¹, R², and R³ is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each of R¹, R², R⁶, and R⁷ is as defined above and described in classes and subclasses herein.

In certain embodiments, R⁶ and R⁷ are each independently an optionally substituted group selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; phenyl, and 8-10-membered aryl. In some embodiments, R⁶ and R⁷ are each independently an optionally substituted C₁₋₂₀ aliphatic. In some embodiments, R⁶ and R⁷ are each independently an optionally substituted C₁₋₂₀ heteroaliphatic having. In some embodiments, R⁶ and R⁷ are each independently an optionally substituted phenyl or 8-10-membered aryl. In some embodiments, R⁶ and R⁷ are each independently an optionally substituted 5- to 10-membered heteroaryl. In some embodiments, R⁶ and R⁷ can be taken together with intervening atoms to form one or more rings selected from the group consisting of: optionally substituted C₃-C₁₄ carbocycle, optionally substituted C₃-C₁₄ heterocycle, optionally substituted C₆-C₁₀ aryl, and optionally substituted 5- to 10-membered heteroaryl. In some embodiments, R⁶ and R⁷ are each independently an optionally substituted C₁₋₆ aliphatic. In some embodiments, each occurrence of R⁶ and R⁷ is independently methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, or benzyl. In some embodiments, each occurrence of R⁶ and R⁷ is independently perfluoro. In some embodiments, each occurrence of R⁶ and R⁷ is independently —CF₂CF₃.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹, R², and R³ is independently as defined above and described in classes and subclasses herein.

In some embodiments, an activating functional group is

wherein each R¹ and R² is independently as defined above and described in classes and subclasses herein.

Counterions

In certain embodiments, X is any anion. In certain embodiments, X is a nucleophile. In some embodiments, X is a nucleophile capable of ring opening an epoxide. In certain embodiments, X is absent. In certain embodiments, X is a nucleophilic ligand. Exemplary nucleophilic ligands include, but are not limited to, —OR^(x), —SR^(x), —O(C═O)R^(x), —O(C═O)OR^(x), —O(C═O)N(R^(x))₂, —N(R^(x))C═O)R^(x), —NC, —CN, halo (e.g., —Br, —I, —Cl), —N₃, —O(SO₂)R^(x) and —OPR^(x) ₃, wherein each R^(x) is, independently, selected from hydrogen, optionally substituted aliphatic, optionally substituted heteroaliphatic, optionally substituted aryl and optionally substituted heteroaryl.

In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is selected from optionally substituted aliphatic, fluorinated aliphatic, optionally substituted heteroaliphatic, optionally substituted aryl, fluorinated aryl, and optionally substituted heteroaryl.

For example, in certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substituted aliphatic. In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substituted alkyl and fluoroalkyl. In certain embodiments, X is —O(C═O)CH₃ or —O(C═O)CF₃.

Furthermore, in certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substituted aryl, fluoroaryl, or heteroaryl. In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substituted aryl. In certain embodiments, X is —O(C═O)R^(x), wherein R^(x) is optionally substituted phenyl. In certain embodiments, X is —O(C═O)C₆H₅ or —O(C═O)C₆F₅.

In certain embodiments, X is —OR^(x), wherein R^(x) is selected from optionally substituted aliphatic, optionally substituted heteroaliphatic, optionally substituted aryl, and optionally substituted heteroaryl.

For example, in certain embodiments, X is —OR^(x), wherein R^(x) is optionally substituted aryl. In certain embodiments, X is —OR^(x), wherein R^(x) is optionally substituted phenyl. In certain embodiments, X is —OC₆H₅ or —OC₆H₂(2,4-NO₂).

In certain embodiments, X is halo. In certain embodiments, X is —Br. In certain embodiments, X is —Cl. In certain embodiments, X is —I.

In certain embodiments, X is —O(SO₂)R^(x). In certain embodiments X is —OTs. In certain embodiments X is —OSO₂Me. In certain embodiments X is —OSO₂CF₃. In some embodiments, X is a 2,4-dinitrophenolate anion.

II.c. Phosphorous-Containing Activating Groups

In some embodiments, activating functional groups Z are phosphorous containing groups.

In certain embodiments, a phosphorous-containing functional group is chosen from the group consisting of: phosphines (—PR^(y) ₂); Phosphine oxides —P(O)R^(y) ₂; phosphinites P(OR⁴)R^(y) ₂; phosphonites P(OR⁴)₂R^(y); phosphites P(OR⁴)₃; phosphinates OP(OR⁴)R^(y) ₂; phosphonates; OP(OR⁴)₂R^(y); phosphates —OP(OR⁴)₃; phosponium salts ([—PR^(y) ₃]⁺) where a phosphorous-containing functional group may be linked to a metal complex through any available position (e.g. direct linkage via the phosphorous atom, or in some cases via an oxygen atom).

In certain embodiments, a phosphorous-containing functional group is chosen from the group consisting of:

or a combination of two or more of these

-   -   wherein each R¹, R², and R⁴ is as defined above and described in         classes and subclasses herein; and where two R⁴ groups can be         taken together with intervening atoms to form an optionally         substituted ring optionally containing one or more heteroatoms,         or an R⁴ group can be taken with an R¹ or R² group to an         optionally substituted carbocyclic, heterocyclic, heteroaryl, or         aryl ring.

In some embodiments, phosphorous containing functional groups include those disclosed in The Chemistry of Organophosphorus Compounds. Volume 4. Ter- and Quinquevalent Phosphorus Acids and their Derivatives. The Chemistry of Functional Group Series Edited by Frank R. Hartley (Cranfield University, Cranfield, U.K.). Wiley: New York. 1996. ISBN 0-471-95706-2, the entirety of which is hereby incorporated herein by reference.

In certain embodiments, phosphorous containing functional groups have the formula:

-(V)_(b)-[(R⁹R¹⁰R¹¹P)⁺]_(n)W^(n-), wherein:

-   V is —O—, —N═, or —NR^(z)—, -   b is 1 or 0, -   each of R⁹, R¹⁰ and R¹¹ are independently present or absent and, if     present, are independently selected from the group consisting of     optionally substituted C₁-C₂₀ aliphatic, optionally substituted     phenyl, optionally substituted C₈-C₁₄ aryl, optionally substituted     3- to 14-membered heterocyclic, optionally substituted 5- to     14-membered heteroaryl, halogen, ═O, —OR^(z), ═NR^(z), and N(R^(z))₂     where R^(z) is hydrogen, or an optionally substituted C₁-C₂₀     aliphatic, optionally substituted phenyl, optionally substituted 8-     to 14-membered aryl, optionally substituted 3- to 14-membered     heterocyclic, or optionally substituted 5- to 14-membered     heteroaryl, -   W is any anion, and -   n is an integer between 1 and 4.

In some embodiments, an activating functional group is a phosphonate group:

wherein each R¹, R², and R⁴ is independently as defined above and described in classes and subclasses herein.

In specific embodiments, a phosphonate activating functional group is selected from the group consisting of:

In some embodiments, an activating functional group is a phosphonic diamide group:

wherein each R¹, R², and R⁴ is independently as defined above and described in classes and subclasses herein. In certain embodiments, each R¹ and R² group in a phosphonic diamide is methyl.

In some embodiments, an activating functional group is a phosphine group:

wherein R¹, and R² are as defined above and described in classes and subclasses herein.

In some embodiments, a phosphine activating functional group is selected from the group consisting of:

In some embodiments, the present invention provides bimetallic complexes and methods of using the same, wherein:

i) an activating group is

ii) an activating group is

iii) an activating group is

iv) an activating group is

v) an activating group is

vi) an activating group is

vii) an activating group is

viii) an activating group is selected from the group consisting of

ix) an activating group is

x) an activating group is

xi) an activating group is

xii) an activating group is

xiii) an activating group is

xiv) an activating group is

xv) an activating group is

xvi) an activating group is

xvii) an activating group is

xviii) an activating group is

xix) an activating group is

xx) an activating group is

xxi) an activating group is

xxii) an activating group is

xxiii) an activating group is

xxiv) an activating group is

xxv) an activating group is

xxvi) an activating group

xxvii) an activating group is

xxviii) an activating group is

xxix) an activating group is

xxx) an activating group is

xxxi) an activating group is

xxxii) for subsets i) through xxxi), each R¹ group is the same;

xxxiii) for subsets i) through xxxi), each R¹ group is hydrogen;

xxxiv) for subsets i) through xxxi), at least one R¹ group is different from other R¹ groups;

xxxv) for subsets i) through xxxi), R¹ is optionally substituted C₁₋₂₀ aliphatic;

xxxvi) for subsets i) through xxxi), each R¹ is independently hydrogen, —CF₂CF₃, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionally substituted phenyl, or optionally substituted benzyl;

xxxvii) for subsets i) through xxxvi), each R² group is the same;

xxxviii) for subsets i) through xxxvi), each R² group is hydrogen;

xxxix) for subsets i) through xxxvi), at least one R² group is different from other R² groups;

xl) for subsets i) through xxxvi), R² is optionally substituted C₁₋₂₀ aliphatic;

xli) for subsets i) through xxxvi), each R² is independently hydrogen, —CF₂CF₃, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionally substituted phenyl, or optionally substituted benzyl;

xlii) for subsets i) through xli), R¹ and R² are the same;

xliii) for subsets i) through xli) R¹ and R² are taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings;

xliv) for any of subsets i) through xliii) having R³, R³ is hydrogen;

xlv) for any of subsets i) through xliii) having R³, R³ is optionally substituted C₁₋₂₀ aliphatic;

xlvi) for any of subsets i) through xliii) having R³, R³ is independently hydrogen, —CF₂CF₃, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, optionally substituted phenyl, or optionally substituted benzyl;

xlvii) for any of subsets i) through xliii) having R³, one or more R¹ or R² groups are taken together with R³ and intervening atoms to form an optionally substituted heterocyclic or heteroaryl ring;

xlviii) for any of subsets i) through xlviii) having R⁴, R⁴ is hydrogen;

xlix) for any of subsets i) through xlviii) having R⁴, R⁴ is optionally substituted C₁₋₁₂ aliphatic;

l) for any of subsets i) through xlviii) having R⁴, R¹ and R⁴ are taken together with intervening atoms to form one or more optionally substituted heterocyclic or heteroaryl rings optionally containing one or more additional heteroatoms;

li) for subsets xvi) and xvii), Ring A is a 5- to 6-membered heteroaryl group;

lii) for subset li), R⁵ is hydroxyl;

liii) for subset li), R⁵ is optionally substituted C₁₋₂₀ aliphatic;

liv) for subsets i) through xxxi) where an activating group is cationic, X is acetate;

Iv) for subsets i) through xxxi) where an activating group is cationic, X is trifluoroacetate;

lvi) for subsets i) through xxxi) where an activating group is cationic, X is optionally substituted benzoate;

lvii) for subsets i) through xxxi) where an activating group is cationic, X is phenoxide;

lviii) for subsets i) through xxxi) where an activating group is cationic, X is dinitrophenoxide;

lvix) for subsets i) through xxxi) where an activating group is cationic, X is halo.

It will be appreciated that for each of the classes and subclasses described above and herein, all possible combinations of the variables described in subsets i) through lvix) above are contemplated by the present invention. Thus, the invention encompasses any and all compounds of the formulae described above and herein, and subclasses thereof, generated by taking any possible combination of variables set forth herein (including, but not limited to subsets i) through lvix)).

III. Metal Complexes

In certain embodiments, the present invention provides metal complexes that include two metal atoms coordinated to a multidentate ligand system and at least one activating moiety tethered to a ligand.

In some embodiments, provided metal complexes have a structure C-1:

wherein:

-   -   M¹ is a first metal atom;     -   M² is a second metal atom;

comprises a multidentate ligand system capable of coordinating both metal atoms;

-   -   represents one or more activating moieties attached to the         multidentate ligand system, where         is a linker moiety covalently coupled to the ligand system, each         Z is an activating functional group; and m is an integer from 1         to 4 representing the number of Z groups present on an         individual linker moiety.

In certain embodiments, provided metal complexes include two metal atoms coordinated to a multidentate ligand system and at least one activating moiety tethered to a multidentate ligand system. In some embodiments, there are 1 to 10 activating moieties

tethered to a multidentate ligand. In certain embodiments, there are 1 to 8 such activating moieties tethered to a multidentate ligand. In certain embodiments, there are 1 to 4 such activating moieties tethered to the multidentate ligand.

Syntheses of multidentate ligand systems are known in the art and include those described by Kember et al. Macromolecules 2010, 43, 2291-2298, and WO 2007/091616, the entire contents of each of which are hereby incorporated by reference. For example, in some embodiments a multidentate ligand is formed by reacting two equivalents of a dialdehyde (optionally comprising a

activating moiety) with two equivalents of a diamine (optionally comprising a

activating moiety). Such multidentate ligands may be combined (in some embodiments in situ) with two equivalents of a metal ion to form a bimetallic complex.

Additional synthetic procedures for the synthesis of mono-metal complexes with tethered activating moieties are found in WO 2010/022388, the entire contents of which are hereby incorporated by reference.

III.a. Metal Atoms

In certain embodiments, M¹ is a metal atom selected from periodic table groups 3-13, inclusive. In certain embodiments, M¹ is a transition metal selected from periodic table groups 5-12, inclusive. In certain embodiments, M¹ is a transition metal selected from periodic table groups 4-11, inclusive. In certain embodiments, M¹ is a transition metal selected from periodic table groups 5-10, inclusive. In certain embodiments, M¹ is a transition metal selected from periodic table groups 7-9, inclusive. In some embodiments, M¹ is selected from the group consisting of Cr, Mn, V, Fe, Co, Mo, W, Ru, Al, and Ni. In some embodiments, M¹ is a metal atom selected from the group consisting of: cobalt; chromium; aluminum; titanium; ruthenium, and manganese. In some embodiments, M¹ is cobalt. In some embodiments, M¹ is chromium. In some embodiments, M¹ is aluminum. In some embodiments, M¹ is zinc.

In certain embodiments, M² is a metal atom selected from periodic table groups 3-13, inclusive. In certain embodiments, M² is a transition metal selected from periodic table groups 5-12, inclusive. In certain embodiments, M² is a transition metal selected from periodic table groups 4-11, inclusive. In certain embodiments, M² is a transition metal selected from periodic table groups 5-10, inclusive. In certain embodiments, M² is a transition metal selected from periodic table groups 7-9, inclusive. In some embodiments, M² is selected from the group consisting of Cr, Mn, V, Fe, Co, Mo, W, Ru, Al, and Ni. In some embodiments, M² is a metal atom selected from the group consisting of: cobalt; chromium; aluminum; titanium; ruthenium, and manganese. In some embodiments, M² is cobalt. In some embodiments, M² is chromium. In some embodiments, M² is aluminum. In some embodiments, M² is zinc.

In certain embodiments, M¹ and M² are the same metal. In other embodiments, M¹ and M² are different metals. In some embodiments, M¹ and M² are both cobalt. In some embodiments, M¹ and M² are both chromium. In some embodiments, M¹ and M² are both aluminum. In some embodiments, M¹ and M² are both zinc.

In certain embodiments, a metal complex is dicobalt complex. In certain embodiments where the metal complex is a dicobalt complex, each cobalt atom has an oxidation state of 3+(i.e., Co(III)). In some embodiments, at least one cobalt metal has an oxidation state of 2+(i.e., Co(II)). In some embodiments, when the metal complex is a dicobalt complex, one cobalt atom has an oxidation state of 3+(i.e., Co(III)) and the other cobalt atom has an oxidation state of 2+(i.e., Co(II)).

II.b. Ligands

In some embodiments, a metal complex

comprises two metal atoms coordinated to a single multidentate ligand system and in some embodiments, a metal complex comprises a chelate containing a plurality of individual ligands. In certain embodiments, a metal complex contains at least one bidentate ligand.

In some embodiments, a metal complex contains at least one tridentate ligand. In some embodiments, a metal complex contains at least one tetradentate ligand. In some embodiments, a metal complex contains a hexadentate ligand.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   Q¹, Q², Q³, Q³, Q⁴, Q⁵ and Q⁶ are each independently oxygen,     nitrogen or sulfur atoms which may be optionally substituted if     allowed by valency rules; -   each     is optionally present and independently represents an optionally     substituted bridge containing 2 to 20 carbon atoms, wherein such     bridges can independently, or in combination, optionally form one or     more optionally substituted rings, wherein each bridge present     optionally contains one or more heteroatoms; and -   one or more     groups is optionally substituted with one or more     ; -   wherein each     is independently an activating moiety as defined above and described     in classes and subclasses herein.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   Q¹, Q², Q³, Q⁴, Q⁵, Q⁶, and     are independently as defined above and described in classes and     subclasses herein; and -   each

moiety is independently an optionally substituted carbon bridge that is optionally unsaturated, where any carbon atoms comprising the bridge may be part of one or more optionally substituted rings.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   Q¹, Q², Q³, Q³, Q⁴, Q⁵, Q⁶ and     are independently as defined above and described in classes and     subclasses herein; -   rings C and D each independently represent an optionally substituted     5- to 12-membered mono- or polycylic ring that may be saturated,     partially unsaturated or aromatic and may optionally contain one or     more heteroatoms; -   each R^(e) is independently selected from the group consisting of     hydrogen; a     group; or an optionally substituted moiety selected from the group     consisting of: C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to     8-membered saturated or partially unsaturated monocyclic carbocycle;     a 7- to 14-membered saturated or partially unsaturated polycyclic     carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4     heteroatoms independently selected from nitrogen, oxygen, or sulfur;     an 8- to 14-membered polycyclic heteroaryl ring having 1-5     heteroatoms independently selected from nitrogen, oxygen, or sulfur,     a 3- to 8-membered saturated or partially unsaturated monocyclic     heterocyclic ring having 1-3 heteroatoms independently selected from     nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or     partially unsaturated polycyclic heterocycle having 1-5 heteroatoms     independently selected from nitrogen, oxygen, or sulfur; phenyl; or     an 8- to 14-membered polycyclic aryl ring; wherein if two R^(e)     groups are present on the same position, they may be taken together     to form a spirocyclic ring optionally containing one or more     heteroatoms and optionally substituted with one or more R^(c) groups     (as defined below); and -   q is 1 or 2.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   Q¹, Q², Q³, Q³, Q⁴, Q⁵, Q⁶, R^(e), and     are independently as defined above and described in classes and     subclasses herein; and -   each R^(a) and R^(b) is independently a substituent present on     phenyl rings where two or more R^(a) groups and/or two or more R^(b)     groups may be taken together to form one or more optionally     substituted rings.

In certain embodiments, R^(a) and R^(b) are independently selected from the group consisting of: a

group, halogen, —NO₂, —CN, —SR^(y), —S(O)R^(y), —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO, —N₃, —OR⁴, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y), —NR^(y)C(O)OR^(y); or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; where two or more adjacent R^(a) or R^(b) groups can be taken together to form an optionally substituted saturated, partially unsaturated, or aromatic 5- to 12-membered ring containing 0 to 4 heteroatoms;

-   wherein each R^(y) and R⁴ is independently as defined above and     described in classes and subclasses herein.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   -   Q¹, Q², Q³, Q³, Q⁴, Q⁵, Q⁶, R^(a), R^(b) and R^(c), are         independently as defined above and described in classes and         subclasses herein; and     -   h and i are independently 1, 2, 3, or 4; and     -   each R^(c) and R^(d) is independently selected from the group         consisting of: a         group, halogen, —OR⁷, —N(R^(y))₂, —SR⁷, —CN, —NO₂, —SO₂R^(y),         —SOR, —SO₂N(R^(y))₂; —CNO, —NR^(y)SO₂R^(y), —NCO, —N₃, —SiR₃; or         an optionally substituted radical selected from the group         consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to         8-membered saturated or partially unsaturated monocyclic         carbocycle; a 7- to 14-membered saturated or partially         unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic         heteroaryl ring having 1-4 heteroatoms independently selected         from nitrogen, oxygen, or sulfur; an 8- to 14-membered         polycyclic heteroaryl ring having 1-5 heteroatoms independently         selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered         saturated or partially unsaturated monocyclic heterocyclic ring         having 1-3 heteroatoms independently selected from nitrogen,         oxygen, or sulfur; a 6- to 14-membered saturated or partially         unsaturated polycyclic heterocycle having 1-5 heteroatoms         independently selected from nitrogen, oxygen, or sulfur, phenyl;         or an 8- to 14-membered polycyclic aryl ring; where two or more         R^(c) or R^(d) groups may be taken together with the carbon         atoms to which they are attached and any intervening atoms to         form one or more optionally substituted rings; and where when         two R^(c) or R^(d) groups are attached to the same carbon atom,         they may be taken together with the carbon atom to which they         are attached to form a moiety selected from the group consisting         of: a 3- to 8-membered spirocyclic ring, a carbonyl group, an         optionally substituted alkene, an optionally substituted oxime,         an optionally substituted hydrazone, and an optionally         substituted imine.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   -   Q¹, Q², Q³, Q³, Q⁴, Q⁵, Q⁶ R^(a), R^(b), R^(c), R^(d) and R^(e)         are as defined above and described in classes and subclasses         herein.

In certain embodiments, a multidentate ligand system in complexes of formula C1 has a structure

where:

-   -   R^(a), R^(b), R^(c), R^(d) and R^(e) are independently as         defined above and described in classes and subclasses herein;         and     -   R¹² is optionally present, and if present is selected from the         group consisting of: a         group; or an optionally substituted radical selected from the         group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; and         phenyl.

In certain embodiments, at least one activating moiety is tethered to only one phenyl ring of a ligand, as shown in formula I:

-   -   where         , M₁, M², R¹², R^(a), R^(b), R^(c), R^(d), and R^(e) are         independently as defined above and described in classes and         subclasses herein;     -   X¹ and X² are each independently an anion or a nucleophile         capable of ring opening an epoxide; and     -   where one or more activating moieties         present on the indicated phenyl ring in any one or more         available positions as valency allows.

It will be appreciated that, depending on the metal ion(s) selected and their oxidation state, additional counterion X groups and/or metals may be present. Alternatively or additionally, one or more X groups may interact with multiple metal centers. For example, the following formulae are contemplated by the present invention:

In certain embodiments, at least one activating moiety is tethered to two phenyl rings of a ligand, as shown in formula II:

-   -   where         , M¹, M², R¹, R^(a), R^(b), R^(c), R^(d), R^(e), X¹, and X² are         independently as defined above and described in classes and         subclasses herein; and     -   where one or more activating moieties         are present on each phenyl ring in any one or more available         positions as valency allows.

In certain embodiments of formulae described above, at least one phenyl ring of a ligand is independently selected from the group consisting of:

wherein each

is independently an activating moiety bonded to any one or more unsubstituted positions of a phenyl ring.

In certain embodiments, there is one

group on each aryl ring in a position meta to the phenoxy group. In certain embodiments of complexes having formulae described above, at least one of the phenyl rings of a metal complex is independently selected from the group consisting of:

In certain embodiments both of the phenyl rings in ligands having the formula

are substituted at one meta position as shown above. In certain embodiments, such ligands exist as a mixture of regioisiomers while in other embodiments, the ligands comprise substantially a single regioisomer.

In certain embodiments, there are two

group on each aryl ring in a position meta to the phenoxy group. In certain embodiments of complexes having formulae described above, at least one of the phenyl rings of a metal complex is independently selected from the group consisting of:

In certain embodiments, there is one

group on each aryl ring in a position para to the phenoxy group. In certain embodiments of complexes having formulae described above, at least one of the phenyl rings of a metal complex is independently selected from the group consisting of:

In certain embodiments, there is one

group on a benzyl position of the phenyl ring. In certain embodiments of formulae described above, a metal complex comprises at least one moiety independently selected from the group consisting of:

As indicated above, two phenyl rings contained in a ligand structure need not be the same. Though not explicitly shown in certain formulae above, it is to be understood that a catalyst may have an activating moiety attached to different positions on each of the two rings, and such compounds are specifically encompassed within the scope of the present invention. Furthermore, activating moieties can be present on multiple parts of the ligand, for instance activating moieties can be present on the diamine bridge and on one or both phenyl rings in the same catalyst.

In certain embodiments, at least one activating moiety is tethered to a diamine bridge of a ligand, as shown in formula III-a, III-b, and III-c:

wherein each of R^(a), R^(b), R^(c), R^(d), R^(e), Z, m, M¹, M², X¹, X², and R¹² is independently as defined above and described in classes and subclasses herein.

In certain embodiments, at least one activating moiety is tethered to a diamine bridge of a ligand, as shown in formula IV-a, IV-b, and IV-c:

wherein each of R^(a), R^(b), R^(c), R^(d), R^(e), Z, m, M¹, M², X¹, X², and R¹² is independently as defined above and described in classes and subclasses herein.

In certain embodiments, at least one activating moiety is tethered to a cyclic diamine bridge of a ligand, as shown in formula V-a, V-b, and V-c:

wherein each of R^(a), R^(b), R^(e), R^(d), R^(e), Z, m, M¹, M², X¹, X², and R¹² is independently as defined above and described in classes and subclasses herein.

In certain embodiments, at least one activating moiety is tethered to a cyclic diamine bridge of a ligand, as shown in formula VI-a, VI-b, and VI-c:

wherein each of R^(a), R^(b), R^(c), R^(d), R^(e), Z, m, M¹, M², X¹, X², and R¹² is independently as defined above and described in classes and subclasses herein.

In some embodiments, provided metal complexes are of formula VII-a through VII-e:

wherein each of X¹ and X², if present, is independently as defined above and described in classes and subclasses herein; and each of R^(c), R^(d), R^(e), Z, m, M¹, and M² is independently as defined above and described in classes and subclasses herein.

In certain embodiments, metal complexes of the present invention include, but are not limited to those in Table 1 below:

wherein each M is independently as described above for M¹ or M².

In certain embodiments, for complexes of Table 1, M¹ and M² is Co—X, where X is as defined above and described in classes and subclasses herein. In certain embodiments, for complexes of Table 1, M¹ and M² is Co—OC(O)CF₃. In certain embodiments, for complexes of Table 1, M¹ and M² is Co—OAc. In certain embodiments, for complexes of Table 1, M¹ and M² is Co—OC(O)C₆F₅. In certain embodiments, for complexes of Table 1, M¹ and M² is Co—N₃. In certain embodiments, for complexes of Table 1, M¹ and M² is Co—Cl. In certain embodiments, for complexes of Table 1, M¹ and M² is Co-nitrophenoxy. In certain embodiments, for complexes of Table 1, M¹ and M² is Co-dinitrophenoxy. In some embodiments, for complexes of Table 1, M¹ and M² is Cr—X.

IV. Polymers

In some embodiments, the present disclosure provides methods of polymerization comprising contacting an epoxide with carbon dioxide in the presence of a provided metal complex to form a polycarbonate. In some embodiments, the present invention provides a method of polymerization, the method comprising:

-   -   a) providing an epoxide of formula:

-   -   -   wherein:         -   R^(a′) is hydrogen or an optionally substituted radical             selected from the group consisting of C₁₋₃₀ aliphatic; C₁₋₃₀             heteroaliphatic; phenyl; a 3- to 8-membered saturated or             partially unsaturated monocyclic carbocycle, a 7-14 carbon             saturated, partially unsaturated or aromatic polycyclic             carbocycle; a 5- to 6-membered monocyclic heteroaryl ring             having 1-4 heteroatoms independently selected from nitrogen,             oxygen, or sulfur; a 3- to 8-membered saturated or partially             unsaturated heterocyclic ring having 1-3 heteroatoms             independently selected from nitrogen, oxygen, or sulfur; a             6- to 12-membered polycyclic saturated or partially             unsaturated heterocycle having 1-5 heteroatoms independently             selected from nitrogen, oxygen, or sulfur; or an 8- to             10-membered bicyclic heteroaryl ring having 1-5 heteroatoms             independently selected from nitrogen, oxygen, or sulfur, and         -   each of R^(b′), R^(c′), and R^(d′) is independently hydrogen             or an optionally substituted radical selected from the group             consisting of C₁₋₁₂ aliphatic; C₁₋₁₂ heteroaliphatic;             phenyl; a 3- to 8-membered saturated or partially             unsaturated monocyclic carbocycle, a 7-14 carbon saturated,             partially unsaturated or aromatic polycyclic carbocycle; a             5- to 6-membered monocyclic heteroaryl ring having 1-4             heteroatoms independently selected from nitrogen, oxygen, or             sulfur; a 3- to 8-membered saturated or partially             unsaturated heterocyclic ring having 1-3 heteroatoms             independently selected from nitrogen, oxygen, or sulfur; a             6- to 12-membered polycyclic saturated or partially             unsaturated heterocycle having 1-5 heteroatoms independently             selected from nitrogen, oxygen, or sulfur; or an 8- to             10-membered bicyclic heteroaryl ring having 1-5 heteroatoms             independently selected from nitrogen, oxygen, or sulfur;         -   wherein any of (R^(a′) and R^(c′)), (R^(c′) and R^(d′)), and             (R^(a′) and R^(b′)) can be taken together with intervening             atoms to form one or more optionally substituted rings;

    -   b) contacting the epoxide and carbon dioxide in the presence of         a metal complex as described herein to provide a polymer having         a formula selected from the group consisting of:

In some embodiments, a provided polymer has a formula:

In some embodiments, a provided polymer has a formula:

In some embodiments, carbon dioxide is optional and a provided polymer has a formula:

In certain embodiments, R^(b′), R^(c′), and R^(d′) are each hydrogen. In some embodiments, R^(a′) is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R^(a′) is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, the epoxide is ethylene oxide, propylene oxide, or cyclohexene oxide.

In certain embodiments, one of R^(a′), R^(b′), R^(c′), and R^(d′) is hydrogen. In certain embodiments, two of R^(e′), R^(b′), R^(c′), and R^(d′) are hydrogen. In certain embodiments, three of R^(a′), R^(b′), R^(c′), and R^(d′) are hydrogen.

In certain embodiments, R^(a′) is hydrogen. In certain embodiments, R^(b′) is hydrogen. In certain embodiments, R^(a′) is hydrogen. In certain embodiments, R^(d′) is hydrogen.

In certain embodiments, R^(a′), R^(b′), R^(c′), and R^(d′) are each independently an optionally substituted C₁₋₃₀ aliphatic group. In certain embodiments, R^(a′), R^(b′), R^(c′), and R^(d′) are each independently an optionally substituted C₁₋₂₀ aliphatic group. In certain embodiments, R^(a′), R^(b′), R^(c′), and R^(d′) are each independently an optionally substituted C₁₋₁₂ aliphatic group. In certain embodiments, R^(a′), Rb, R^(c′), and R^(d′) are each independently an optionally substituted C₁₋₈ aliphatic group. In certain embodiments, R^(a′), R^(b′), R^(c′), and R^(d′) are each independently an optionally substituted C₃₋₈ aliphatic group. In certain embodiments, R^(a′), R^(b′), R^(c′), and R^(d′) are each independently an optionally substituted C₃₋₁₂ aliphatic group.

In certain embodiments, R^(a′) is an optionally substituted C₁₋₃₀ aliphatic group. In certain embodiments, R^(b′) is an optionally substituted C₁₋₃₀ aliphatic group. In certain embodiments, R^(c′) is an optionally substituted C₁₋₃₀ aliphatic group. In certain embodiments, R^(d′) is an optionally substituted C₁₋₃₀ aliphatic group.

In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form one or more optionally substituted 3-12-membered carbocyclic rings. In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form a polycyclic carbocycle comprising two or more optionally substituted 3-8-membered carbocyclic rings. In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form a polycyclic carbocycle comprising two or more optionally substituted 5-7-membered carbocyclic rings.

In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form a bicyclic carbocycle comprising two optionally substituted 3-12-membered carbocyclic rings. In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form a bicyclic carbocycle comprising two optionally substituted 3-8-membered carbocyclic rings. In some embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form a bicyclic carbocycle comprising two optionally substituted 5-7-membered carbocyclic rings.

In certain embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form an optionally substituted 3-12-membered carbocyclic ring. In certain embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form an optionally substituted 3-8-membered carbocyclic ring. In certain embodiments, an R^(a′) and an R^(b′) attached to the same carbon are taken together to form an optionally substituted 5-7-membered carbocyclic ring.

In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form one or more optionally substituted 3-12-membered carbocyclic rings. In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form a polycyclic carbocycle comprising two or more optionally substituted 3-8-membered carbocyclic rings. In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form a polycyclic carbocycle comprising two or more optionally substituted 5-7-membered carbocyclic rings.

In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form a bicyclic carbocycle comprising two optionally substituted 3-12-membered carbocyclic rings. In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form a bicyclic carbocycle comprising two optionally substituted 3-8-membered carbocyclic rings. In some embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form a bicyclic carbocycle comprising two optionally substituted 5-7-membered carbocyclic rings.

In certain embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form an optionally substituted 3-12-membered carbocyclic ring. In certain embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form an optionally substituted 3-8-membered carbocyclic ring. In certain embodiments, an R^(b′) and an R^(c′) attached to adjacent carbons are taken together to form an optionally substituted 5-7-membered carbocyclic ring.

In certain embodiments, the polymer comprises a copolymer of two different repeating units where R^(a′), R^(b′), and R^(c′) of the two different repeating units are not all the same. In some embodiments, a polymer comprises a copolymer of three or more different repeating units wherein R^(a′), R^(b′), and R^(c′) of each of the different repeating units are not all the same as R^(a′), R^(b′), and R^(c′) of any of the other different repeating units. In some embodiments, a polymer is a random copolymer. In some embodiments, a polymer is a tapered copolymer.

In some embodiments, a polymer contains a metal complex as described herein. In some embodiments, a polymer comprises residue of a metal complex as described herein. In some embodiments, a polymer comprises a salt of an organic cation and X, wherein X is a nucleophile or counterion. In some embodiments, X is 2,4-dinitrophenolate anion.

In some embodiments, R^(a′) is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R^(a′) is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, R^(a′) is optionally substituted phenyl. In some embodiments, R^(a′) is optionally substituted 8- to 10-membered aryl. In some embodiments, R^(a′) is optionally substituted 5- to 10-membered heteroaryl. In some embodiments, R^(a′) is optionally substituted 3- to 7-membered heterocyclic.

In certain embodiments, R^(a′) is selected from methyl, ethyl, propyl, butyl, vinyl, allyl, phenyl, trifluoromethyl,

or any two or more of the above. In certain embodiments, R^(a′) is methyl. In certain embodiments, R^(a′) is ethyl. In certain embodiments, R^(a′) is propyl. In certain embodiments, R^(a′) is butyl. In certain embodiments, R^(a′) is vinyl. In certain embodiments, R^(a′) is allyl. In certain embodiments, R^(a′) is phenyl. In certain embodiments, R^(a′) is trifluoromethyl. In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In certain embodiments, R^(a′) is

In some embodiments, R^(b′) is hydrogen. In some embodiments, R^(b′) is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R^(b′) is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, R^(b′) is optionally substituted phenyl. In some embodiments, R^(b′) is optionally substituted 8- to 10-membered aryl. In some embodiments, R^(b′) is optionally substituted 5- to 10-membered heteroaryl. In some embodiments, R^(b′) is optionally substituted 3- to 7-membered heterocyclic.

In some embodiments, R^(c′) is hydrogen. In some embodiments, R^(c′) is optionally substituted C₁₋₁₂ aliphatic. In some embodiments, R^(c′) is optionally substituted C₁₋₁₂ heteroaliphatic. In some embodiments, R^(c′) is optionally substituted phenyl. In some embodiments, R^(c′) is optionally substituted 8- to 10-membered aryl. In some embodiments, R^(c′) is optionally substituted 5- to 10-membered heteroaryl. In some embodiments, R^(c′) is optionally substituted 3- to 7-membered heterocyclic.

In some embodiments, R^(a′) and R^(c′) are taken together with intervening atoms to form one or more rings selected from the group consisting of: optionally substituted C₃-C₁₄ carbocycle, optionally substituted 3- to 14-membered heterocycle, optionally substituted phenyl, optionally substituted C₈-C₁₀ aryl, and optionally substituted 5- to 10-membered heteroaryl.

In some embodiments, R^(b′) and R^(c′) are taken together with intervening atoms to form one or more rings selected from the group consisting of: optionally substituted C₃-C₁₄ carbocycle, optionally substituted 3- to 14-membered heterocycle, optionally substituted phenyl, optionally substituted C₈-C₁₀ aryl, and optionally substituted 5- to 10-membered heteroaryl.

In some embodiments, R^(a′) and R^(b′) are taken together with intervening atoms to form one or more rings selected from the group consisting of: optionally substituted C₃-C₁₄ carbocycle, optionally substituted 3- to 14-membered heterocycle, optionally substituted phenyl, optionally substituted C₈-C₁₀ aryl, and optionally substituted 5- to 10-membered heteroaryl.

In some embodiments, the invention includes methods for synthesizing polyethers from epoxides. Suitable methods of performing these reactions are disclosed in U.S. Pat. No. 7,399,822, the entire contents of which are hereby incorporated herein by reference.

In some embodiments, the invention includes methods for synthesizing cyclic carbonates from carbon dioxide and epoxides using catalysts described above, suitable methods of performing this reaction are disclosed in U.S. Pat. No. 6,870,004, which is incorporated herein by reference.

While we have described a number of embodiments of this invention, it is apparent that our basic examples may be altered to provide other embodiments that utilize the compounds and methods of this invention. Therefore, it will be appreciated that the scope of this invention is to be defined by the appended claims rather than by the specific embodiments that have been presented by way of example. 

What is claimed is:
 1. A method comprising the step of contacting an epoxide and carbon dioxide with a bimetallic complex having the structure:

wherein: M¹ is a first metal atom; M² is a second metal atom;

comprises a multidentate ligand system capable of coordinating both metal atoms;

represents one or more activating moieties attached to the multidentate ligand system, where

is a linker moiety covalently coupled to the ligand system, m is an integer from 1 to 4 representing the number of Z groups present on an individual linker moiety; and each (Z) is an activating functional group independently selected from the group consisting of:

wherein: each R¹ and R² is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein R¹ and R² can be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more additional heteroatoms; each R³ is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein an R³ group can be taken with an R¹ or R² group to form one or more optionally substituted rings; and each R⁴ is independently hydrogen, a hydroxyl protecting group, or an optionally substituted radical selected from the group consisting of C₁₋₂₀ acyl; C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; R⁵ is R² or hydroxyl; wherein R¹ and R⁵ can be taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings; each R⁶ and R⁷ is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein R⁶ and R⁷ can be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms, and an R⁶ and R⁷ group can be taken with an R¹ or R² group to form one or more optionally substituted rings; each occurrence of R⁸ is independently selected from the group consisting of: halogen, —NO₂, —CN, —SR^(y), —S(O)R^(y), —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO, —N₃, —OR⁷, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y), —NR^(y)C(O)OR^(y); or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; and where two or more adjacent R⁸ groups can be taken together to form an optionally substituted saturated, partially unsaturated, or aromatic 5- to 12-membered ring containing 0 to 4 heteroatoms; each R^(y) is independently —H, or an optionally substituted radical selected from the group consisting of C₁₋₆ aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5-6 membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, and 8- to 10-membered aryl; X⁻ is any anion; Ring A is an optionally substituted, 5- to 10-membered heteroaryl group; and Ring B is an optionally substituted, 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 0-2 heteroatoms in addition to the depicted ring nitrogen atom independently selected from nitrogen, oxygen, or sulfur.
 2. The method of claim 1, wherein M¹ and M² are independently selected from the group consisting of Cr, Mn, V, Fe, Co, Mo, W, Ru, Al, and Ni.
 3. The method of claim 1, wherein M¹ and M² are independently selected from the group consisting of: Co, Al, and Cr.
 4. The method of claim 1, wherein M¹ and M² are Co.
 5. The method of claim 1, wherein M¹ and M² Cr.
 6. The method of claim 1, wherein M¹ and M² are Al.
 7. The method of claim 1, wherein the

moiety contains 1-30 atoms including at least one carbon atom, and optionally one or more atoms selected from the group consisting of N, O, S, Si, B, and P.
 8. The method of claim 1, wherein the

moiety is a C₂₋₃₀ aliphatic group wherein one or more methylene units are optionally and independently replaced by —NR^(y)—, —N(R^(y))C(O)—, —C(O)N(R^(y))—, —O—, —C(O)—, —OC(O)—, —C(O)O—, —S—, —Si(R^(y))₂—, —SO—, —SO₂—, —C(═S)—, —C(═NR^(y))—, or —N═N—.
 9. The method of claim 1, wherein the

moiety is selected from the group consisting of:

wherein each s is independently 0-6, t is 0-4, * represents the site of attachment to a ligand, and each # represents a site of attachment of an activating functional group.
 10. The method of claim 1, wherein the

moiety comprises a hexadentate ligand.
 11. The method of claim 1, wherein the

moiety comprises two tridentate ligands.
 12. The method of claim 10, wherein the hexadentate ligand is selected from the group consisting of salen derivatives, derivatives of salen ligands, bis-2-hydroxybenzamido derivatives, and Robson-type macrocyclic Schiff bases.
 13. The method of claim 10, wherein the hexadentate ligand is selected from the group consisting of:

wherein: Q¹, Q², Q³, Q³, Q⁴, Q⁵ and Q⁶ are each independently oxygen, nitrogen or sulfur atoms which may be optionally substituted if allowed by valency rules; each

is optionally present and independently represents an optionally substituted bridge containing 2 to 20 carbon atoms, wherein such bridges can independently, or in combination, optionally form one or more optionally substituted rings, wherein each bridge present optionally contains one or more heteroatoms; each

moiety is independently an optionally substituted carbon bridge that is optionally unsaturated, where any carbon atoms comprising the bridge may be part of one or more optionally substituted rings; one or more

groups is optionally substituted with one or more

; rings C and D each independently represent an optionally substituted 5- to 12-membered mono- or polycylic ring that may be saturated, partially unsaturated or aromatic and may optionally contain one or more heteroatoms; each R^(a) and R^(b) is independently a substituent present on phenyl rings where two or more R^(a) groups and/or two or more R^(b) groups may be taken together to form one or more optionally substituted rings; each R^(c) and R^(d) is independently selected from the group consisting of: a

group, halogen, —OR⁷, —N(R^(y))₂, —SR⁷, —CN, —NO₂, —SO₂R^(y), —SOR, —SO₂N(R^(y))₂; —CNO, —NR^(y)SO₂R^(y), —NCO, —N₃, —SiR₃; or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; where two or more R^(c) or R^(d) groups may be taken together with the carbon atoms to which they are attached and any intervening atoms to form one or more optionally substituted rings; and where when two R^(c) or R^(d) groups are attached to the same carbon atom, they may be taken together with the carbon atom to which they are attached to form a moiety selected from the group consisting of: a 3- to 8-membered spirocyclic ring, a carbonyl group, an optionally substituted alkene, an optionally substituted oxime, an optionally substituted hydrazone, and an optionally substituted imine; each R^(e) is independently selected from the group consisting of hydrogen; a

group; or an optionally substituted moiety selected from the group consisting of: C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein if two R^(e) groups are present on the same position, they may be taken together to form a spirocyclic ring optionally containing one or more heteroatoms and optionally substituted with one or more R^(e) groups; R¹² is optionally present, and if present is selected from the group consisting of: a

group; or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; and phenyl; h and i are independently 1, 2, 3, or 4; and q is 1 or
 2. 14. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide; and where one or more activating moieties

are present on the indicated phenyl ring in any one or more available positions as valency allows.
 15. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide; and where one or more activating moieties

are present on the indicated phenyl ring in any one or more available positions as valency allows.
 16. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 17. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 18. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 19. The method of claim 13, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 20. The method of claim 13, wherein the bimetallic complex comprises:

wherein each of X¹ and X², if present, is independently an anion or a nucleophile capable of ring opening an epoxide
 21. The method of claim 1, wherein the bimetallic complex is selected from those in Table 1, wherein each M is independently a metal ion.
 22. The method of claim 21, wherein each M is cobalt.
 23. The method of claim 13, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


24. The method of claim 23, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


25. The method of claim 13, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


26. The method of claim 13, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


27. The method of claim 13, wherein the bimetallic complex comprises at least one moiety independently selected from the group consisting of:


28. The method of any of claims 23 to 27, wherein one or more Z group is independently a neutral functional group selected from the group consisting of amines, phosphines, gaunidines, bis-guanidines, amidines, and nitrogen-containing heterocycles.
 29. The method of any of claims 23 to 27, wherein one or more Z group is a cationic moiety independently selected from the group consisting of:


30. The method of any of claims 23 to 27, wherein each linker moiety

is independently selected from the group consisting of:

wherein each s is independently 0-6, t is 0-4, * represents the site of attachment to a ligand, and each # represents a site of attachment of an activating functional group.
 31. The method of any of claims 23 to 27, wherein M¹ and M² are selected from the group consisting of cobalt, aluminum, and chromium.
 32. The method of any of claims 23 to 27, wherein M¹ and M² are selected from the group consisting of cobalt and chromium.
 33. The method of any of claims 23 to 27, wherein M¹ and M² are cobalt.
 34. The method of any of claims 23 to 27, wherein X is selected from the group consisting of: chlorine, bromine, an optionally substituted C₁₋₁₂ carboxylate, azide, an optionally substituted phenoxide, a sulfonate salt, and a combination of any two or more of these.
 35. The method of any of claims 23 to 27, wherein X is selected from the group consisting of chloride, acetate, trifluoroacetate, azide, pentafluorobenzoate, and a nitrophenolate.
 36. The method of claim 1, wherein the bimetallic complex contains a total of 1 to 8 Z groups.
 37. The method of claim 1, wherein the bimetallic complex contains a total of 1 to 6 Z groups.
 38. The method of claim 1, wherein the bimetallic complex contains a total of 1 to 4 Z groups.
 39. The method of claim 1, wherein the bimetallic complex contains a total of 2 Z groups.
 40. The method of claim 1, wherein the bimetallic complex contains a total of 4 Z groups.
 41. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


42. The method of claim 1, wherein at least one Z group is


43. The method of claim 42, wherein R¹ and R² are optionally substituted C₁₋₂₀ aliphatic.
 44. The method of claim 42, wherein R¹ and R² are optionally substituted C₁₋₁₀ aliphatic.
 45. The method of claim 42, wherein R¹ and R² are taken together to form an optionally substituted ring optionally containing additional heteroatoms.
 46. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


47. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


48. The method of claim 47, wherein R¹ and R² are —H or optionally substituted C₁₋₂₀ aliphatic.
 49. The method of claim 47, wherein R¹ and R² are —H or optionally substituted C₁₋₁₀ aliphatic.
 50. The method of claim 47, wherein R³ is —H or optionally substituted C₁₋₁₀ aliphatic.
 51. The method of claim 47, wherein two or more of R¹, R², and R³ are taken together to form an optionally substituted ring optionally containing additional heteroatoms.
 52. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


53. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


54. The method of claim 53, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₂₀ aliphatic.
 55. The method of claim 53, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₁₀ aliphatic.
 56. The method of claim 53, wherein two or more of R¹ and R² are taken together to form one or more optionally substituted rings optionally containing additional heteroatoms.
 57. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


58. The method of claim 1, wherein at least one Z group is


59. The method of claim 58, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₂₀ aliphatic.
 60. The method of claim 58, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₁₀ aliphatic.
 61. The method of claim 58, wherein two or more of R¹ and R² are taken together to form one or more optionally substituted rings optionally containing additional heteroatoms.
 62. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


63. The method of claim 1, wherein at least one Z group is selected from the group consisting of:


64. The method of claim 1, wherein the epoxide has the formula:

wherein: R^(a′) is hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₃₀ aliphatic; C₁₋₃₀ heteroaliphatic; phenyl; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle, a 7-14 carbon saturated, partially unsaturated or aromatic polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 12-membered polycyclic saturated or partially unsaturated heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or an 8- to 10-membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, and each of R^(b′), R^(c′), and R^(d′) is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₁₂ aliphatic; C₁₋₁₂ heteroaliphatic; phenyl; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle, a 7-14 carbon saturated, partially unsaturated or aromatic polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 12-membered polycyclic saturated or partially unsaturated heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; or an 8- to 10-membered bicyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; wherein any of (R^(a′) and R^(c′)), (R^(c′) and R^(d′)), and (R^(a′) and R^(b′)) can be taken together with intervening atoms to form one or more optionally substituted rings.
 65. The method of claim 64, wherein a polymer formed has a formula selected from the group consisting of:


66. The method of claim 64, wherein R^(b′), R^(c′), and R^(d′) are each hydrogen.
 67. The method of claim 64, wherein R^(a′) is optionally substituted C₁₋₁₂ aliphatic.
 68. The method of claim 1, wherein the epoxide is selected from the group consisting of: ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, 1,2 octene oxide, 3-vinyl cyclohexene oxide, epichlorohydrin and mixtures of any two or more of these.
 69. The method of claim 1, wherein the epoxide is ethylene oxide, propylene oxide, or cyclohexene oxide.
 70. The method of claim 1, wherein the epoxide is propylene oxide.
 71. The method of claim 1, wherein the CO₂ pressure is between about 50 and 800 psi.
 72. The method of claim 1, wherein the ratio of catalyst to epoxide is between about 1:1000 and about 1:100,000.
 73. The method of claim 1, further comprising the steps of letting the polymerization proceed until a desired polymer molecular weight has been achieved, quenching the polymerization reaction and isolating the polymer.
 74. A bimetallic complex having the structure:

wherein: M¹ is a first metal atom; M² is a second metal atom;

comprises a multidentate ligand system capable of coordinating both metal atoms;

represents one or more activating moieties attached to the multidentate ligand system, where

is a linker moiety covalently coupled to the ligand system, m is an integer from 1 to 4 representing the number of Z groups present on an individual linker moiety; and each (Z) is an activating functional group independently selected from the group consisting of:

wherein: each R¹ and R² is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein R¹ and R² can be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more additional heteroatoms; each R³ is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein an R³ group can be taken with an R¹ or R² group to form one or more optionally substituted rings; and each R⁴ is independently hydrogen, a hydroxyl protecting group, or an optionally substituted radical selected from the group consisting of C₁₋₂₀ acyl; C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; R⁵ is R² or hydroxyl; wherein R¹ and R⁵ can be taken together with intervening atoms to form one or more optionally substituted carbocyclic, heterocyclic, aryl, or heteroaryl rings; each R⁶ and R⁷ is independently hydrogen or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein R⁶ and R⁷ can be taken together with intervening atoms to form one or more optionally substituted rings optionally containing one or more heteroatoms, and an R⁶ and R⁷ group can be taken with an R¹ or R² group to form one or more optionally substituted rings; each occurrence of R⁸ is independently selected from the group consisting of: halogen, —NO₂, —CN, —SR^(y), —S(O)R^(y), —S(O)₂R^(y), —NR^(y)C(O)R^(y), —OC(O)R^(y), —CO₂R^(y), —NCO, —N₃, —OR⁷, —OC(O)N(R^(y))₂, —N(R^(y))₂, —NR^(y)C(O)R^(y), —NR^(y)C(O)OR^(y); or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur, an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, phenyl; or an 8- to 14-membered polycyclic aryl ring; and where two or more adjacent R⁸ groups can be taken together to form an optionally substituted saturated, partially unsaturated, or aromatic 5- to 12-membered ring containing 0 to 4 heteroatoms; each R^(y) is independently —H, or an optionally substituted radical selected from the group consisting of C₁₋₆ aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5-6 membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, and 8- to 10-membered aryl; X⁻ is any anion; Ring A is an optionally substituted, 5- to 10-membered heteroaryl group; and Ring B is an optionally substituted, 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 0-2 heteroatoms in addition to the depicted ring nitrogen atom independently selected from nitrogen, oxygen, or sulfur.
 75. The bimetallic complex of claim 74, wherein M¹ and M² are independently selected from the group consisting of Cr, Mn, V, Fe, Co, Mo, W, Ru, Al, and Ni.
 76. The bimetallic complex of claim 74, wherein M¹ and M² are independently selected from the group consisting of: Co, Al, and Cr.
 77. The bimetallic complex of claim 74, wherein M¹ and M² are Co.
 78. The bimetallic complex of claim 74, wherein M¹ and M² Cr.
 79. The bimetallic complex of claim 74, wherein M¹ and M² are Al.
 80. The bimetallic complex of claim 74, wherein the

moiety contains 1-30 atoms including at least one carbon atom, and optionally one or more atoms selected from the group consisting of N, O, S, Si, B, and P.
 81. The bimetallic complex of claim 74, wherein the

moiety is a C₂₋₃₀ aliphatic group wherein one or more methylene units are optionally and independently replaced by —NR^(y)—, —N(R^(y))C(O)—, —C(O)N(R^(y))—, —O—, —C(O)—, —OC(O)—, —C(O)O—, —S—, —Si(R^(y))₂—, —SO—, —SO₂—, —C(═S)—, —C(═NR^(y))—, or —N═N—, wherein each occurrence of R^(y) is independently —H, or an optionally substituted radical selected from the group consisting of C₁₋₆ aliphatic, phenyl, a 3-7 membered saturated or partially unsaturated carbocyclic ring, a 3-7 membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-2 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 5-6 membered heteroaryl ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, and 8- to 10-membered aryl.
 82. The bimetallic complex of claim 74, wherein the

moiety is selected from the group consisting of:

wherein each s is independently 0-6, t is 0-4, * represents the site of attachment to a ligand, and each # represents a site of attachment of an activating functional group.
 83. The bimetallic complex of claim 74, wherein the

moiety comprises a hexadentate ligand.
 84. The bimetallic complex of claim 74, wherein the

moiety comprises two tridentate ligands.
 85. The bimetallic complex of claim 83, wherein the hexadentate ligand is selected from the group consisting of salen derivatives, derivatives of salen ligands, bis-2-hydroxybenzamido derivatives, and Robson-type macrocyclic Schiff bases.
 86. The bimetallic complex of claim 83, wherein the hexadentate ligand is selected from the group consisting of:

wherein: Q¹, Q², Q³, Q³, Q⁴, Q⁵ and Q⁶ are each independently oxygen, nitrogen or sulfur atoms which may be optionally substituted if allowed by valency rules; each

is optionally present and independently represents an optionally substituted bridge containing 2 to 20 carbon atoms, wherein such bridges can independently, or in combination, optionally form one or more optionally substituted rings, wherein each bridge present optionally contains one or more heteroatoms; each

moiety is independently an optionally substituted carbon bridge that is optionally unsaturated, where any carbon atoms comprising the bridge may be part of one or more optionally substituted rings; one or more

groups is optionally substituted with one or more

; rings C and D each independently represent an optionally substituted 5- to 12-membered mono- or polycylic ring that may be saturated, partially unsaturated or aromatic and may optionally contain one or more heteroatoms; each R^(a) and R^(b) is independently a substituent present on phenyl rings where two or more R^(a) groups and/or two or more R^(b) groups may be taken together to form one or more optionally substituted rings; each R^(c) and R^(d) is independently selected from the group consisting of: a

group, halogen, —OR⁷, —N(R^(y))₂, —SR⁷, —CN, —NO₂, —SO₂R^(y), —SOR, —SO₂N(R^(y))₂; —CNO, —NR^(y)SO₂R^(y), —NCO, —N₃, —SiR₃; or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur; a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; where two or more R^(c) or R^(d) groups may be taken together with the carbon atoms to which they are attached and any intervening atoms to form one or more optionally substituted rings; and where when two R^(c) or R^(d) groups are attached to the same carbon atom, they may be taken together with the carbon atom to which they are attached to form a moiety selected from the group consisting of: a 3- to 8-membered spirocyclic ring, a carbonyl group, an optionally substituted alkene, an optionally substituted oxime, an optionally substituted hydrazone, and an optionally substituted imine; each R^(e) is independently selected from the group consisting of hydrogen; a

group; or an optionally substituted moiety selected from the group consisting of: C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; a 3- to 8-membered saturated or partially unsaturated monocyclic carbocycle; a 7- to 14-membered saturated or partially unsaturated polycyclic carbocycle; a 5- to 6-membered monocyclic heteroaryl ring having 1-4 heteroatoms independently selected from nitrogen, oxygen, or sulfur; an 8- to 14-membered polycyclic heteroaryl ring having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 3- to 8-membered saturated or partially unsaturated monocyclic heterocyclic ring having 1-3 heteroatoms independently selected from nitrogen, oxygen, or sulfur, a 6- to 14-membered saturated or partially unsaturated polycyclic heterocycle having 1-5 heteroatoms independently selected from nitrogen, oxygen, or sulfur; phenyl; or an 8- to 14-membered polycyclic aryl ring; wherein if two R^(e) groups are present on the same position, they may be taken together to form a spirocyclic ring optionally containing one or more heteroatoms and optionally substituted with one or more R^(e) groups; R¹² is optionally present, and if present is selected from the group consisting of: a

group; or an optionally substituted radical selected from the group consisting of C₁₋₂₀ aliphatic; C₁₋₂₀ heteroaliphatic; and phenyl; h and i are independently 1, 2, 3, or 4; and q is 1 or
 2. 87. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide; and where one or more activating moieties

are present on the indicated phenyl ring in any one or more available positions as valency allows.
 88. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide; and where one or more activating moieties

are present on the indicated phenyl ring in any one or more available positions as valency allows.
 89. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 90. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 91. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 92. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein: X¹ and X² are each independently an anion or a nucleophile capable of ring opening an epoxide.
 93. The bimetallic complex of claim 86, wherein the bimetallic complex comprises:

wherein each of X¹ and X², if present, independently an anion or a nucleophile capable of ring opening an epoxide.
 94. The bimetallic complex of claim 74, wherein the bimetallic complex is selected from those in Table 1, wherein each M is independently a metal ion.
 95. The bimetallic complex of claim 94, wherein each M is cobalt.
 96. The bimetallic complex of claim 86, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


97. The bimetallic complex of claim 96, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


98. The bimetallic complex of claim 86, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


99. The bimetallic complex of claim 86, at least one phenyl ring of a bimetallic complex is independently selected from the group consisting of:


100. The bimetallic complex of claim 86, wherein the bimetallic complex comprises at least one moiety independently selected from the group consisting of:


101. The bimetallic complex of any of claims 96 to 100, wherein one or more Z group is independently a neutral functional group selected from the group consisting of amines, phosphines, gaunidines, bis-guanidines, amidines, and nitrogen-containing heterocycles.
 102. The bimetallic complex of any of claims 96 to 100, wherein one or more Z group is a cationic moiety independently selected from the group consisting of:


103. The bimetallic complex of any of claims 96 to 100, wherein each linker moiety “

” is independently selected from the group consisting of:

wherein each s is independently 0-6, t is 0-4, * represents the site of attachment to a ligand, and each # represents a site of attachment of an activating functional group.
 104. The bimetallic complex of any of claims 96 to 100, wherein M¹ and M² are selected from the group consisting of cobalt, aluminum, and chromium.
 105. The bimetallic complex of any of claims 96 to 100, wherein M¹ and M² are selected from the group consisting of cobalt and chromium.
 106. The bimetallic complex of any of claims 96 to 100, wherein M¹ and M² are cobalt.
 107. The bimetallic complex of any of claims 96 to 100, wherein X is selected from the group consisting of: chlorine, bromine, an optionally substituted C₁₋₁₂ carboxylate, azide, an optionally substituted phenoxide, a sulfonate salt, and a combination of any two or more of these.
 108. The bimetallic complex of any of claims 96 to 100, wherein X is selected from the group consisting of chloride, acetate, trifluoroacetate, azide, pentafluorobenzoate, and a nitrophenolate.
 109. The bimetallic complex of claim 1, wherein the bimetallic complex contains a total of 1 to 8 Z groups.
 110. The bimetallic complex of claim 1, wherein the bimetallic complex contains a total of 1 to 6 Z groups.
 111. The bimetallic complex of claim 74, wherein the bimetallic complex contains a total of 1 to 4 Z groups.
 112. The bimetallic complex of claim 74, wherein the bimetallic complex contains a total of 2 Z groups.
 113. The bimetallic complex of claim 74, wherein the bimetallic complex contains a total of 4 Z groups.
 114. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


115. The bimetallic complex of claim 74, wherein at least one Z group is


116. The bimetallic complex of claim 115, wherein R¹ and R² are optionally substituted C₁₋₂₀ aliphatic.
 117. The bimetallic complex of claim 115, wherein R¹ and R² are optionally substituted C₁₋₁₀ aliphatic.
 118. The bimetallic complex of claim 115, wherein R¹ and R² are taken together to form an optionally substituted ring optionally containing additional heteroatoms.
 119. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


120. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


121. The bimetallic complex of claim 120, wherein R¹ and R² are —H or optionally substituted C₁₋₂₀ aliphatic.
 122. The bimetallic complex of claim 120, wherein R¹ and R² are —H or optionally substituted C₁₋₁₀ aliphatic.
 123. The bimetallic complex of claim 120, wherein R³ is —H or optionally substituted C₁₋₁₀ aliphatic.
 124. The bimetallic complex of claim 120, wherein two or more of R¹, R², and R³ are taken together to form an optionally substituted ring optionally containing additional heteroatoms.
 125. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


126. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


127. The bimetallic complex of claim 126, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₂₀ aliphatic.
 128. The bimetallic complex of claim 126, wherein each R¹ and R² is independently —H or optionally substituted C₁₋₁₀ aliphatic.
 129. The bimetallic complex of claim 126, wherein two or more of R¹ and R² are taken together to form one or more optionally substituted rings optionally containing additional heteroatoms.
 130. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


131. The bimetallic complex of claim 74, wherein at least one Z group is


132. The bimetallic complex of claim 131, wherein each R¹ and R² is independently independently —H or optionally substituted C₁₋₂₀ aliphatic.
 133. The bimetallic complex of claim 131, wherein each R¹ and R² is independently independently —H or optionally substituted C₁₋₁₀ aliphatic.
 134. The bimetallic complex of claim 131, wherein two or more of R¹ and R² are taken together to form one or more optionally substituted rings optionally containing additional heteroatoms.
 135. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of:


136. The bimetallic complex of claim 74, wherein at least one Z group is selected from the group consisting of: 